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File System Guide

Red Hat Ceph Storage 7

Configuring and Mounting Ceph File Systems

Red Hat Ceph Storage Documentation Team

Abstract

This guide describes how to configure the Ceph Metadata Server (MDS) and how to create, mount, and work the Ceph File System (CephFS).
Red Hat is committed to replacing problematic language in our code, documentation, and web properties. We are beginning with these four terms: master, slave, blacklist, and whitelist. Because of the enormity of this endeavor, these changes will be implemented gradually over several upcoming releases. For more details, see our CTO Chris Wright's message.

Chapter 1. Introduction to the Ceph File System
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As a storage administrator, you can gain an understanding of the features, system components, and limitations to manage a Ceph File System (CephFS) environment.

1.1. Ceph File System features and enhancements
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The Ceph File System (CephFS) is a file system compatible with POSIX standards that is built on top of Ceph’s distributed object store, called RADOS (Reliable Autonomic Distributed Object Storage). CephFS provides file access to a Red Hat Ceph Storage cluster, and uses the POSIX semantics wherever possible. For example, in contrast to many other common network file systems like NFS, CephFS maintains strong cache coherency across clients. The goal is for processes using the file system to behave the same when they are on different hosts as when they are on the same host. However, in some cases, CephFS diverges from the strict POSIX semantics.

The Ceph File System has the following features and enhancements:

Scalability
The Ceph File System is highly scalable due to horizontal scaling of metadata servers and direct client reads and writes with individual OSD nodes.
Shared File System
The Ceph File System is a shared file system so multiple clients can work on the same file system at once.
Multiple File Systems
You can have multiple file systems active on one storage cluster. Each CephFS has its own set of pools and its own set of Metadata Server (MDS) ranks. When deploying multiple file systems this requires more running MDS daemons. This can increase metadata throughput, but also increases operational costs. You can also limit client access to certain file systems.
High Availability
The Ceph File System provides a cluster of Ceph Metadata Servers (MDS). One is active and others are in standby mode. If the active MDS terminates unexpectedly, one of the standby MDS becomes active. As a result, client mounts continue working through a server failure. This behavior makes the Ceph File System highly available. In addition, you can configure multiple active metadata servers.
Configurable File and Directory Layouts
The Ceph File System allows users to configure file and directory layouts to use multiple pools, pool namespaces, and file striping modes across objects.
POSIX Access Control Lists (ACL)
The Ceph File System supports the POSIX Access Control Lists (ACL). ACLs are enabled by default with the Ceph File Systems mounted as kernel clients with kernel version kernel-3.10.0-327.18.2.el7 or newer. To use an ACL with the Ceph File Systems mounted as FUSE clients, you must enable them.
Client Quotas
The Ceph File System supports setting quotas on any directory in a system. The quota can restrict the number of bytes or the number of files stored beneath that point in the directory hierarchy. CephFS client quotas are enabled by default.
Important

CephFS EC pools are for archival purpose only.

Additional Resources

1.2. Ceph File System components
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The Ceph File System has two primary components:

Clients
The CephFS clients perform I/O operations on behalf of applications using CephFS, such as ceph-fuse for FUSE clients and kcephfs for kernel clients. CephFS clients send metadata requests to an active Metadata Server. In return, the CephFS client learns of the file metadata, and can begin safely caching both metadata and file data.
Metadata Servers (MDS)

The MDS does the following:

  • Provides metadata to CephFS clients.
  • Manages metadata related to files stored on the Ceph File System.
  • Coordinates access to the shared Red Hat Ceph Storage cluster.
  • Caches hot metadata to reduce requests to the backing metadata pool store.
  • Manages the CephFS clients' caches to maintain cache coherence.
  • Replicates hot metadata between active MDS.
  • Coalesces metadata mutations to a compact journal with regular flushes to the backing metadata pool.
  • CephFS requires at least one Metadata Server daemon (ceph-mds) to run.

The diagram below shows the component layers of the Ceph File System.

157 Ceph File System 1021 2
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157 Ceph File System 1021 2

The bottom layer represents the underlying core storage cluster components:

  • Ceph OSDs (ceph-osd) where the Ceph File System data and metadata are stored.
  • Ceph Metadata Servers (ceph-mds) that manages Ceph File System metadata.
  • Ceph Monitors (ceph-mon) that manages the master copy of the cluster map.

The Ceph Storage protocol layer represents the Ceph native librados library for interacting with the core storage cluster.

The CephFS library layer includes the CephFS libcephfs library that works on top of librados and represents the Ceph File System.

The top layer represents two types of Ceph clients that can access the Ceph File Systems.

The diagram below shows more details on how the Ceph File System components interact with each other.

157 Ceph File System 1021 1
View larger image
157 Ceph File System 1021 1

Additional Resources

1.3. Ceph File System and SELinux
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Starting with Red Hat Enterprise Linux 8.3 and Red Hat Ceph Storage 4.2, support for using Security-Enhanced Linux (SELinux) on Ceph File Systems (CephFS) environments is available. You can now set any SELinux file type with CephFS, along with assigning a particular SELinux type on individual files. This support applies to the Ceph File System Metadata Server (MDS), the CephFS File System in User Space (FUSE) clients, and the CephFS kernel clients.

Additional Resources

  • See the Using SELinux on Red Hat Enterprise Linux 8 for more information about SELinux.

The Ceph File System diverges from the strict POSIX semantics in the following ways:

  • If a client’s attempt to write a file fails, the write operations are not necessarily atomic. That is, the client might call the write() system call on a file opened with the O_SYNC flag with an 8MB buffer and then terminates unexpectedly and the write operation can be only partially applied. Almost all file systems, even local file systems, have this behavior.
  • In situations when the write operations occur simultaneously, a write operation that exceeds object boundaries is not necessarily atomic. For example, writer A writes "aa|aa" and writer B writes "bb|bb" simultaneously, where "|" is the object boundary, and "aa|bb" is written rather than the proper "aa|aa" or "bb|bb".
  • POSIX includes the telldir() and seekdir() system calls that allow you to obtain the current directory offset and seek back to it. Because CephFS can fragment directories at any time, it is difficult to return a stable integer offset for a directory. As such, calling the seekdir() system call to a non-zero offset might often work but is not guaranteed to do so. Calling seekdir() to offset 0 will always work. This is equivalent to the rewinddir() system call.
  • Sparse files propagate incorrectly to the st_blocks field of the stat() system call. CephFS does not explicitly track parts of a file that are allocated or written to, because the st_blocks field is always populated by the quotient of file size divided by block size. This behavior causes utilities, such as du, to overestimate used space.
  • When the mmap() system call maps a file into memory on multiple hosts, write operations are not coherently propagated to caches of other hosts. That is, if a page is cached on host A, and then updated on host B, host A page is not coherently invalidated.
  • CephFS clients present a hidden .snap directory that is used to access, create, delete, and rename snapshots. Although this directory is excluded from the readdir() system call, any process that tries to create a file or directory with the same name returns an error. The name of this hidden directory can be changed at mount time with the -o snapdirname=.<new_name> option or by using the client_snapdir configuration option.

Additional Resources

Chapter 3. Deployment of the Ceph File System
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As a storage administrator, you can deploy Ceph File Systems (CephFS) in a storage environment and have clients mount those Ceph File Systems to meet the storage needs.

Basically, the deployment workflow is three steps:

  1. Create Ceph File Systems on a Ceph Monitor node.
  2. Create a Ceph client user with the appropriate capabilities, and make the client key available on the node where the Ceph File System will be mounted.
  3. Mount CephFS on a dedicated node, using either a kernel client or a File System in User Space (FUSE) client.

Prerequisites

  • A running, and healthy Red Hat Ceph Storage cluster.
  • Installation and configuration of the Ceph Metadata Server daemon (ceph-mds).

These user capabilities can help you restrict access to a Ceph File System (CephFS) based on the needed requirements.

Important

All user capability flags, except rw, must be specified in alphabetical order.

Layouts and Quotas

When using layouts or quotas, clients require the p flag, in addition to rw capabilities. Setting the p flag restricts all the attributes being set by special extended attributes, those with a ceph. prefix. Also, this restricts other means of setting these fields, such as openc operations with layouts.

Example

client.0
    key: AQAz7EVWygILFRAAdIcuJ10opU/JKyfFmxhuaw==
    caps: [mds] allow rwp
    caps: [mon] allow r
    caps: [osd] allow rw tag cephfs data=cephfs_a

client.1
    key: AQAz7EVWygILFRAAdIcuJ11opU/JKyfFmxhuaw==
    caps: [mds] allow rw
    caps: [mon] allow r
    caps: [osd] allow rw tag cephfs data=cephfs_a
Copy to Clipboard Toggle word wrap

In this example, client.0 can modify layouts and quotas on the file system cephfs_a, but client.1 cannot.

Snapshots

When creating or deleting snapshots, clients require the s flag, in addition to rw capabilities. When the capability string also contains the p flag, the s flag must appear after it.

Example

client.0
    key: AQAz7EVWygILFRAAdIcuJ10opU/JKyfFmxhuaw==
    caps: [mds] allow rw, allow rws path=/temp
    caps: [mon] allow r
    caps: [osd] allow rw tag cephfs data=cephfs_a
Copy to Clipboard Toggle word wrap

In this example, client.0 can create or delete snapshots in the temp directory of file system cephfs_a.

Network

Restricting clients connecting from a particular network.

Example

client.0
  key: AQAz7EVWygILFRAAdIcuJ10opU/JKyfFmxhuaw==
  caps: [mds] allow r network 10.0.0.0/8, allow rw path=/bar network 10.0.0.0/8
  caps: [mon] allow r network 10.0.0.0/8
  caps: [osd] allow rw tag cephfs data=cephfs_a network 10.0.0.0/8
Copy to Clipboard Toggle word wrap

The optional network and prefix length is in CIDR notation, for example, 10.3.0.0/16.

Additional Resources

3.2. Creating Ceph File Systems
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You can create multiple Ceph File Systems (CephFS) on a Ceph Monitor node.

Prerequisites

  • A running, and healthy Red Hat Ceph Storage cluster.
  • Installation and configuration of the Ceph Metadata Server daemon (ceph-mds).
  • Root-level access to a Ceph Monitor node.
  • Root-level access to a Ceph client node.

Procedure

  1. Configure the client node to use the Ceph storage cluster.

    1. Enable the Red Hat Ceph Storage Tools repository:

      Red Hat Enterprise Linux 8

      [root@client01 ~]# subscription-manager repos --enable=rhceph-6-tools-for-rhel-8-x86_64-rpms
      Copy to Clipboard Toggle word wrap

      Red Hat Enterprise Linux 9

      [root@client01 ~]# subscription-manager repos --enable=rhceph-6-tools-for-rhel-9-x86_64-rpms
      Copy to Clipboard Toggle word wrap

    2. Install the ceph-fuse package: 

      [root@client ~]# dnf install ceph-fuse
      Copy to Clipboard Toggle word wrap

    3. Copy the Ceph client keyring from the Ceph Monitor node to the client node:

      Syntax

      scp root@MONITOR_NODE_NAME:/etc/ceph/KEYRING_FILE /etc/ceph/
      Copy to Clipboard Toggle word wrap

      Replace MONITOR_NODE_NAME with the Ceph Monitor host name or IP address.

      Example

      [root@client ~]# scp root@192.168.0.1:/etc/ceph/ceph.client.1.keyring /etc/ceph/
      Copy to Clipboard Toggle word wrap

    4. Copy the Ceph configuration file from a Ceph Monitor node to the client node:

      Syntax

      scp root@MONITOR_NODE_NAME:/etc/ceph/ceph.conf /etc/ceph/ceph.conf
      Copy to Clipboard Toggle word wrap

      Replace MONITOR_NODE_NAME with the Ceph Monitor host name or IP address.

      Example

      [root@client ~]# scp root@192.168.0.1:/etc/ceph/ceph.conf /etc/ceph/ceph.conf
      Copy to Clipboard Toggle word wrap

    5. Set the appropriate permissions for the configuration file: 

      [root@client ~]# chmod 644 /etc/ceph/ceph.conf
      Copy to Clipboard Toggle word wrap

  2. Create a Ceph File System:

    Syntax

    ceph fs volume create FILE_SYSTEM_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph fs volume create cephfs01
    Copy to Clipboard Toggle word wrap

    Repeat this step to create additional file systems.

    Note

    By running this command, Ceph automatically creates the new pools, and deploys a new Ceph Metadata Server (MDS) daemon to support the new file system. This also configures the MDS affinity accordingly.

  3. Verify access to the new Ceph File System from a Ceph client.

    1. Authorize a Ceph client to access the new file system:

      Syntax

      ceph fs authorize FILE_SYSTEM_NAME CLIENT_NAME DIRECTORY PERMISSIONS
      Copy to Clipboard Toggle word wrap

      Example

      [root@mon ~]# ceph fs authorize cephfs01 client.1 / rw
[client.1]
    key = BQAmthpf81M+JhAAiHDYQkMiCq3x+J0n9e8REK==

[root@mon ~]# ceph auth get client.1
exported keyring for client.1
[client.1]
    key = BQAmthpf81M+JhAAiHDYQkMiCq3x+J0n9e8REK==
    caps mds = "allow rw fsname=cephfs01"
    caps mon = "allow r fsname=cephfs01"
    caps osd = "allow rw tag cephfs data=cephfs01"
      Copy to Clipboard Toggle word wrap

      Note

      Optionally, you can add a safety measure by specifying the root_squash option. This prevents accidental deletion scenarios by disallowing clients with a uid=0 or gid=0 to do write operations, but still allows read operations.

      Example

      [root@mon ~]# ceph fs authorize cephfs01 client.1 / rw root_squash /volumes rw
[client.1]
    key = BQAmthpf81M+JhAAiHDYQkMiCq3x+J0n9e8REK==

[root@mon ~]# ceph auth get client.1
[client.1]
    key = BQAmthpf81M+JhAAiHDYQkMiCq3x+J0n9e8REK==
    caps mds = "allow rw fsname=cephfs01 root_squash, allow rw fsname=cephfs01 path=/volumes"
    caps mon = "allow r fsname=cephfs01"
    caps osd = "allow rw tag cephfs data=cephfs01"
      Copy to Clipboard Toggle word wrap

      In this example, root_squash is enabled for the file system cephfs01, except within the /volumes directory tree.

      Important

      The Ceph client can only see the CephFS it is authorized for.

    2. Copy the Ceph user’s keyring to the Ceph client node:

      Syntax

      ceph auth get CLIENT_NAME > OUTPUT_FILE_NAME
scp OUTPUT_FILE_NAME TARGET_NODE_NAME:/etc/ceph
      Copy to Clipboard Toggle word wrap

      Example

      [root@mon ~]# ceph auth get client.1 > ceph.client.1.keyring
exported keyring for client.1
[root@mon ~]# scp ceph.client.1.keyring client:/etc/ceph
root@client's password:
ceph.client.1.keyring                     100%  178   333.0KB/s   00:00
      Copy to Clipboard Toggle word wrap

    3. On the Ceph client node, create a new directory:

      Syntax

      mkdir PATH_TO_NEW_DIRECTORY_NAME
      Copy to Clipboard Toggle word wrap

      Example

      [root@client ~]# mkdir /mnt/mycephfs
      Copy to Clipboard Toggle word wrap

    4. On the Ceph client node, mount the new Ceph File System:

      Syntax

      ceph-fuse PATH_TO_NEW_DIRECTORY_NAME -n CEPH_USER_NAME --client-fs=_FILE_SYSTEM_NAME
      Copy to Clipboard Toggle word wrap

      Example

      [root@client ~]# ceph-fuse /mnt/mycephfs/ -n client.1 --client-fs=cephfs01
ceph-fuse[555001]: starting ceph client
2022-05-09T07:33:27.158+0000 7f11feb81200 -1 init, newargv = 0x55fc4269d5d0 newargc=15
ceph-fuse[555001]: starting fuse
      Copy to Clipboard Toggle word wrap

    5. On the Ceph client node, list the directory contents of the new mount point, or create a file on the new mount point.

By default, Ceph uses replicated pools for data pools. You can also add an additional erasure-coded data pool to the Ceph File System, if needed. Ceph File Systems (CephFS) backed by erasure-coded pools use less overall storage compared to Ceph File Systems backed by replicated pools. While erasure-coded pools use less overall storage, they also use more memory and processor resources than replicated pools.

Important

CephFS EC pools are for archival purpose only.

Important

For production environments, Red Hat recommends using the default replicated data pool for CephFS. The creation of inodes in CephFS creates at least one object in the default data pool. It is better to use a replicated pool for the default data to improve small-object write performance, and to improve read performance for updating backtraces.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • An existing Ceph File System.
  • Pools using BlueStore OSDs.
  • Root-level access to a Ceph Monitor node.
  • Installation of the attr package.

Procedure

  1. Create an erasure-coded data pool for CephFS:

    Syntax

    ceph osd pool create DATA_POOL_NAME erasure
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph osd pool create cephfs-data-ec01 erasure
pool 'cephfs-data-ec01' created
    Copy to Clipboard Toggle word wrap

  2. Verify the pool was added:

    Example

    [root@mon ~]# ceph osd lspools
    Copy to Clipboard Toggle word wrap

  3. Enable overwrites on the erasure-coded pool:

    Syntax

    ceph osd pool set DATA_POOL_NAME allow_ec_overwrites true
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph osd pool set cephfs-data-ec01 allow_ec_overwrites true
set pool 15 allow_ec_overwrites to true
    Copy to Clipboard Toggle word wrap

  4. Verify the status of the Ceph File System:

    Syntax

    ceph fs status FILE_SYSTEM_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph fs status cephfs-ec
cephfs-ec - 14 clients
=========
RANK  STATE              MDS                ACTIVITY     DNS    INOS   DIRS   CAPS
 0    active  cephfs-ec.example.ooymyq  Reqs:    0 /s  8231   8233    891    921
       POOL           TYPE     USED  AVAIL
cephfs-metadata-ec  metadata   787M  8274G
  cephfs-data-ec      data    2360G  12.1T

       STANDBY MDS
cephfs-ec.example.irsrql
cephfs-ec.example.cauuaj
    Copy to Clipboard Toggle word wrap

  5. Add the erasure-coded data pool to the existing CephFS:

    Syntax

    ceph fs add_data_pool FILE_SYSTEM_NAME DATA_POOL_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph fs add_data_pool cephfs-ec cephfs-data-ec01
    Copy to Clipboard Toggle word wrap

    This example adds the new data pool, cephfs-data-ec01, to the existing erasure-coded file system, cephfs-ec.

  6. Verify that the erasure-coded pool was added to the Ceph File System:

    Syntax

    ceph fs status FILE_SYSTEM_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph fs status cephfs-ec
cephfs-ec - 14 clients
=========
RANK  STATE              MDS                ACTIVITY     DNS    INOS   DIRS   CAPS
 0    active  cephfs-ec.example.ooymyq  Reqs:    0 /s  8231   8233    891    921
       POOL           TYPE     USED  AVAIL
cephfs-metadata-ec  metadata   787M  8274G
  cephfs-data-ec      data    2360G  12.1T
 cephfs-data-ec01     data       0   12.1T

       STANDBY MDS
cephfs-ec.example.irsrql
cephfs-ec.example.cauuaj
    Copy to Clipboard Toggle word wrap

  7. Set the file layout on a new directory:

    Syntax

    mkdir PATH_TO_DIRECTORY
setfattr -n ceph.dir.layout.pool -v DATA_POOL_NAME PATH_TO_DIRECTORY
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# mkdir /mnt/cephfs/newdir
[root@mon ~]# setfattr -n ceph.dir.layout.pool -v cephfs-data-ec01 /mnt/cephfs/newdir
    Copy to Clipboard Toggle word wrap

    In this example, all new files created in the /mnt/cephfs/newdir directory inherit the directory layout and places the data in the newly added erasure-coded pool.

Additional Resources

3.4. Creating client users for a Ceph File System
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Red Hat Ceph Storage uses cephx for authentication, which is enabled by default. To use cephx with the Ceph File System, create a user with the correct authorization capabilities on a Ceph Monitor node and make its key available on the node where the Ceph File System will be mounted.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Installation and configuration of the Ceph Metadata Server daemon (ceph-mds).
  • Root-level access to a Ceph Monitor node.
  • Root-level access to a Ceph client node.

Procedure

  1. Log into the Cephadm shell on the monitor node:

    Example

    [root@host01 ~]# cephadm shell
    Copy to Clipboard Toggle word wrap

  2. On a Ceph Monitor node, create a client user:

    Syntax

    ceph fs authorize FILE_SYSTEM_NAME client.CLIENT_NAME /DIRECTORY CAPABILITY [/DIRECTORY CAPABILITY] PERMISSIONS ...
    Copy to Clipboard Toggle word wrap

    • To restrict the client to only writing in the temp directory of filesystem cephfs_a:

      Example

      [ceph: root@host01 /]# ceph fs authorize cephfs_a client.1 / r /temp rw

client.1
  key = AQBSdFhcGZFUDRAAcKhG9Cl2HPiDMMRv4DC43A==
      Copy to Clipboard Toggle word wrap

    • To completely restrict the client to the temp directory, remove the root (/) directory:

      Example

      [ceph: root@host01 /]# ceph fs authorize cephfs_a client.1 /temp rw
      Copy to Clipboard Toggle word wrap

    Note

    Supplying all or asterisk as the file system name grants access to every file system. Typically, it is necessary to quote the asterisk to protect it from the shell.

  3. Verify the created key:

    Syntax

    ceph auth get client.ID
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph auth get client.1

client.1
  key = AQBSdFhcGZFUDRAAcKhG9Cl2HPiDMMRv4DC43A==
  caps mds = "allow r, allow rw path=/temp"
  caps mon = "allow r"
  caps osd = "allow rw tag cephfs data=cephfs_a"
    Copy to Clipboard Toggle word wrap

  4. Copy the keyring to the client.

    1. On the Ceph Monitor node, export the keyring to a file:

      Syntax

      ceph auth get client.ID -o ceph.client.ID.keyring
      Copy to Clipboard Toggle word wrap

      Example

      [ceph: root@host01 /]# ceph auth get client.1 -o ceph.client.1.keyring
exported keyring for client.1
      Copy to Clipboard Toggle word wrap

    2. Copy the client keyring from the Ceph Monitor node to the /etc/ceph/ directory on the client node:

      Syntax

      scp /ceph.client.ID.keyring root@CLIENT_NODE_NAME:/etc/ceph/ceph.client.ID.keyring
      Copy to Clipboard Toggle word wrap

      Replace CLIENT_NODE_NAME with the Ceph client node name or IP.

      Example

      [ceph: root@host01 /]# scp /ceph.client.1.keyring root@client01:/etc/ceph/ceph.client.1.keyring
      Copy to Clipboard Toggle word wrap

  5. From the client node, set the appropriate permissions for the keyring file:

    Syntax

    chmod 644 ceph.client.ID.keyring
    Copy to Clipboard Toggle word wrap

    Example

    [root@client01 ~]# chmod 644 /etc/ceph/ceph.client.1.keyring
    Copy to Clipboard Toggle word wrap

Additional Resources

  • See the Ceph user management chapter in the Red Hat Ceph Storage Administration Guide for more details.

You can mount the Ceph File System (CephFS) as a kernel client, either manually or automatically on system boot.

Important

Clients running on other Linux distributions, aside from Red Hat Enterprise Linux, are permitted but not supported. If issues are found in the CephFS Metadata Server or other parts of the storage cluster when using these clients, Red Hat will address them. If the cause is found to be on the client side, then the issue will have to be addressed by the kernel vendor of the Linux distribution.

Prerequisites

  • Root-level access to a Linux-based client node.
  • Root-level access to a Ceph Monitor node.
  • An existing Ceph File System.

Procedure

  1. Configure the client node to use the Ceph storage cluster.

    1. Enable the Red Hat Ceph Storage 7 Tools repository:

      Red Hat Enterprise Linux 9

      [root@client01 ~]# subscription-manager repos --enable=rhceph-6-tools-for-rhel-9-x86_64-rpms
      Copy to Clipboard Toggle word wrap

    2. Install the ceph-common package: 

      [root@client01 ~]# dnf install ceph-common
      Copy to Clipboard Toggle word wrap

    3. Log into the Cephadm shell on the monitor node:

      Example

      [root@host01 ~]# cephadm shell
      Copy to Clipboard Toggle word wrap

    4. Copy the Ceph client keyring from the Ceph Monitor node to the client node:

      Syntax

      scp /ceph.client.ID.keyring root@CLIENT_NODE_NAME:/etc/ceph/ceph.client.ID.keyring
      Copy to Clipboard Toggle word wrap

      Replace CLIENT_NODE_NAME with the Ceph client host name or IP address.

      Example

      [ceph: root@host01 /]# scp /ceph.client.1.keyring root@client01:/etc/ceph/ceph.client.1.keyring
      Copy to Clipboard Toggle word wrap

    5. Copy the Ceph configuration file from a Ceph Monitor node to the client node:

      Syntax

      scp /etc/ceph/ceph.conf root@CLIENT_NODE_NAME:/etc/ceph/ceph.conf
      Copy to Clipboard Toggle word wrap

      Replace CLIENT_NODE_NAME with the Ceph client host name or IP address.

      Example

      [ceph: root@host01 /]# scp /etc/ceph/ceph.conf root@client01:/etc/ceph/ceph.conf
      Copy to Clipboard Toggle word wrap

    6. From the client node, set the appropriate permissions for the configuration file: 

      [root@client01 ~]# chmod 644 /etc/ceph/ceph.conf
      Copy to Clipboard Toggle word wrap
    7. Choose either automatically or manually mounting.

Manually Mounting

  1. Create a mount directory on the client node:

    Syntax

    mkdir -p MOUNT_POINT
    Copy to Clipboard Toggle word wrap

    Example

    [root@client01 ~]# mkdir -p /mnt/cephfs
    Copy to Clipboard Toggle word wrap

  2. Mount the Ceph File System. To specify multiple Ceph Monitor addresses, separate them with commas in the mount command, specify the mount point, and set the client name:

    Note

    As of Red Hat Ceph Storage 4.1, mount.ceph can read keyring files directly. As such, a secret file is no longer necessary. Just specify the client ID with name=CLIENT_ID, and mount.ceph will find the right keyring file.

    Syntax

    mount -t ceph MONITOR-1_NAME:6789,MONITOR-2_NAME:6789,MONITOR-3_NAME:6789:/ MOUNT_POINT -o name=CLIENT_ID,fs=FILE_SYSTEM_NAME
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    Example

    [root@client01 ~]# mount -t ceph mon1:6789,mon2:6789,mon3:6789:/ /mnt/cephfs -o name=1,fs=cephfs01
    Copy to Clipboard Toggle word wrap

    Note

    You can configure a DNS server so that a single host name resolves to multiple IP addresses. Then you can use that single host name with the mount command, instead of supplying a comma-separated list.

    Note

    You can also replace the Monitor host names with the string :/ and mount.ceph will read the Ceph configuration file to determine which Monitors to connect to.

    Note

    You can set the nowsync option to asynchronously execute file creation and removal on the Red Hat Ceph Storage clusters. This improves the performance of some workloads by avoiding round-trip latency for these system calls without impacting consistency. The nowsync option requires kernel clients with Red Hat Enterprise Linux 9.0 or later.

    Example

    [root@client01 ~]# mount -t ceph mon1:6789,mon2:6789,mon3:6789:/ /mnt/cephfs -o nowsync,name=1,fs=cephfs01
    Copy to Clipboard Toggle word wrap

  3. Verify that the file system is successfully mounted:

    Syntax

    stat -f MOUNT_POINT
    Copy to Clipboard Toggle word wrap

    Example

    [root@client01 ~]# stat -f /mnt/cephfs
    Copy to Clipboard Toggle word wrap

Automatically Mounting

  1. On the client host, create a new directory for mounting the Ceph File System.

    Syntax

    mkdir -p MOUNT_POINT
    Copy to Clipboard Toggle word wrap

    Example

    [root@client01 ~]# mkdir -p /mnt/cephfs
    Copy to Clipboard Toggle word wrap

  2. Edit the /etc/fstab file as follows:

    Syntax

    #DEVICE                                              PATH                      TYPE               OPTIONS
MON_0_HOST:PORT,            MOUNT_POINT          ceph         name=CLIENT_ID,
MON_1_HOST:PORT,                                                         ceph.client_mountpoint=/VOL/SUB_VOL_GROUP/SUB_VOL/UID_SUB_VOL,                                                       fs=FILE_SYSTEM_NAME,
MON_2_HOST:PORT:/q[_VOL_]/SUB_VOL/UID_SUB_VOL,            [ADDITIONAL_OPTIONS]
    Copy to Clipboard Toggle word wrap

    The first column sets the Ceph Monitor host names and the port number.

    The second column sets the mount point

    The third column sets the file system type, in this case, ceph, for CephFS.

    The fourth column sets the various options, such as, the user name and the secret file using the name and secretfile options. You can also set specific volumes, sub-volume groups, and sub-volumes using the ceph.client_mountpoint option.

    Set the _netdev option to ensure that the file system is mounted after the networking subsystem starts to prevent hanging and networking issues. If you do not need access time information, then setting the noatime option can increase performance.

    Set the fifth and sixth columns to zero.

    Example

    #DEVICE         PATH                   TYPE    OPTIONS         DUMP  FSCK
mon1:6789,      /mnt/cephfs            ceph    name=1,            0     0
mon2:6789,                                     ceph.client_mountpoint=/my_vol/my_sub_vol_group/my_sub_vol/0,
mon3:6789:/                                    fs=cephfs01,
                                               _netdev,noatime
    Copy to Clipboard Toggle word wrap

    The Ceph File System will be mounted on the next system boot.

    Note

    As of Red Hat Ceph Storage 4.1, mount.ceph can read keyring files directly. As such, a secret file is no longer necessary. Just specify the client ID with name=CLIENT_ID, and mount.ceph will find the right keyring file.

    Note

    You can also replace the Monitor host names with the string :/ and mount.ceph will read the Ceph configuration file to determine which Monitors to connect to.

Additional Resources

  • See the mount(8) manual page.
  • See the Ceph user management chapter in the Red Hat Ceph Storage Administration Guide for more details on creating a Ceph user.
  • See the Creating Ceph File Systems section of the Red Hat Ceph Storage File System Guide for details.

You can mount the Ceph File System (CephFS) as a File System in User Space (FUSE) client, either manually or automatically on system boot.

Prerequisites

  • Root-level access to a Linux-based client node.
  • Root-level access to a Ceph Monitor node.
  • An existing Ceph File System.

Procedure

  1. Configure the client node to use the Ceph storage cluster.

    1. Enable the Red Hat Ceph Storage 7 Tools repository:

      Red Hat Enterprise Linux 8

      [root@client01 ~]# subscription-manager repos --enable=6-tools-for-rhel-8-x86_64-rpms
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      Red Hat Enterprise Linux 9

      [root@client01 ~]# subscription-manager repos --enable=6-tools-for-rhel-9-x86_64-rpms
      Copy to Clipboard Toggle word wrap

    2. Install the ceph-fuse package: 

      [root@client01 ~]# dnf install ceph-fuse
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    3. Log into the Cephadm shell on the monitor node:

      Example

      [root@host01 ~]# cephadm shell
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    4. Copy the Ceph client keyring from the Ceph Monitor node to the client node:

      Syntax

      scp /ceph.client.ID.keyring root@CLIENT_NODE_NAME:/etc/ceph/ceph.client.ID.keyring
      Copy to Clipboard Toggle word wrap

      Replace CLIENT_NODE_NAME with the Ceph client host name or IP address.

      Example

      [ceph: root@host01 /]# scp /ceph.client.1.keyring root@client01:/etc/ceph/ceph.client.1.keyring
      Copy to Clipboard Toggle word wrap

    5. Copy the Ceph configuration file from a Ceph Monitor node to the client node:

      Syntax

      scp /etc/ceph/ceph.conf root@CLIENT_NODE_NAME:/etc/ceph/ceph.conf
      Copy to Clipboard Toggle word wrap

      Replace CLIENT_NODE_NAME with the Ceph client host name or IP address.

      Example

      [ceph: root@host01 /]# scp /etc/ceph/ceph.conf root@client01:/etc/ceph/ceph.conf
      Copy to Clipboard Toggle word wrap

    6. From the client node, set the appropriate permissions for the configuration file: 

      [root@client01 ~]# chmod 644 /etc/ceph/ceph.conf
      Copy to Clipboard Toggle word wrap
    7. Choose either automatically or manually mounting.

Manually Mounting

  1. On the client node, create a directory for the mount point:

    Syntax

    mkdir PATH_TO_MOUNT_POINT
    Copy to Clipboard Toggle word wrap

    Example

    [root@client01 ~]# mkdir /mnt/mycephfs
    Copy to Clipboard Toggle word wrap

    Note

    If you used the path option with MDS capabilities, then the mount point must be within what is specified by the path.

  2. Use the ceph-fuse utility to mount the Ceph File System.

    Syntax

    ceph-fuse -n client.CLIENT_ID --client_fs FILE_SYSTEM_NAME MOUNT_POINT
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    Example

    [root@client01 ~]# ceph-fuse -n client.1 --client_fs cephfs01 /mnt/mycephfs
    Copy to Clipboard Toggle word wrap

    Note

    If you do not use the default name and location of the user keyring, that is /etc/ceph/ceph.client.CLIENT_ID.keyring, then use the --keyring option to specify the path to the user keyring, for example:

    Example

    [root@client01 ~]# ceph-fuse -n client.1 --keyring=/etc/ceph/client.1.keyring /mnt/mycephfs
    Copy to Clipboard Toggle word wrap

    Note

    Use the -r option to instruct the client to treat that path as its root:

    Syntax

    ceph-fuse -n client.CLIENT_ID MOUNT_POINT -r PATH
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    Example

    [root@client01 ~]# ceph-fuse -n client.1 /mnt/cephfs -r /home/cephfs
    Copy to Clipboard Toggle word wrap

    Note

    If you want to automatically reconnect an evicted Ceph client, then add the --client_reconnect_stale=true option.

    Example

    [root@client01 ~]# ceph-fuse -n client.1 /mnt/cephfs --client_reconnect_stale=true
    Copy to Clipboard Toggle word wrap

  3. Verify that the file system is successfully mounted:

    Syntax

    stat -f MOUNT_POINT
    Copy to Clipboard Toggle word wrap

    Example

    [root@client01 ~]# stat -f /mnt/cephfs
    Copy to Clipboard Toggle word wrap

Automatically Mounting

  1. On the client node, create a directory for the mount point:

    Syntax

    mkdir PATH_TO_MOUNT_POINT
    Copy to Clipboard Toggle word wrap

    Example

    [root@client01 ~]# mkdir /mnt/mycephfs
    Copy to Clipboard Toggle word wrap

    Note

    If you used the path option with MDS capabilities, then the mount point must be within what is specified by the path.

  2. Edit the /etc/fstab file as follows:

    Syntax

    #DEVICE                 PATH           TYPE          OPTIONS                  DUMP  FSCK
HOST_NAME:PORT,     MOUNT_POINT fuse.ceph     ceph.id=CLIENT_ID,        0     0
HOST_NAME:PORT,                                  ceph.client_mountpoint=/VOL/SUB_VOL_GROUP/SUB_VOL/UID_SUB_VOL,
HOST_NAME:PORT:/                                 ceph.client_fs=FILE_SYSTEM_NAME,ceph.name=USERNAME,ceph.keyring=/etc/ceph/KEYRING_FILE,
                                                     [ADDITIONAL_OPTIONS]
    Copy to Clipboard Toggle word wrap

    The first column sets the Ceph Monitor host names and the port number.

    The second column sets the mount point

    The third column sets the file system type, in this case, fuse.ceph, for CephFS.

    The fourth column sets the various options, such as the user name and the keyring using the ceph.name and ceph.keyring options. You can also set specific volumes, sub-volume groups, and sub-volumes using the ceph.client_mountpoint option. To specify which Ceph File System to access, use the ceph.client_fs option. Set the _netdev option to ensure that the file system is mounted after the networking subsystem starts to prevent hanging and networking issues. If you do not need access time information, then setting the noatime option can increase performance. If you want to automatically reconnect after an eviction, then set the client_reconnect_stale=true option.

    Set the fifth and sixth columns to zero.

    Example

    #DEVICE         PATH              TYPE         OPTIONS         DUMP  FSCK
mon1:6789,      /mnt/mycephfs       fuse.ceph    ceph.id=1,         0     0
mon2:6789,                                     ceph.client_mountpoint=/my_vol/my_sub_vol_group/my_sub_vol/0,
mon3:6789:/                                    ceph.client_fs=cephfs01,ceph.name=client.1,ceph.keyring=/etc/ceph/client1.keyring,
                                               _netdev,defaults
    Copy to Clipboard Toggle word wrap

    The Ceph File System will be mounted on the next system boot.

As a storage administrator, you can use Red Hat’s Ceph Container Storage Interface (CSI) to manage Ceph File System (CephFS) exports. This also allows you to use other services, such as OpenStack’s file system service (Manila) by having a common command-line interface to interact with. The volumes module for the Ceph Manager daemon (ceph-mgr) implements the ability to export Ceph File Systems (CephFS).

The Ceph Manager volumes module implements the following file system export abstractions:

  • CephFS volumes
  • CephFS subvolume groups
  • CephFS subvolumes

4.1. Ceph File System volumes
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As a storage administrator, you can create, list, and remove Ceph File System (CephFS) volumes. CephFS volumes are an abstraction for Ceph File Systems.

This section describes how to:

4.1.1. Creating a Ceph file system volume
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Ceph Orchestrator is a module for Ceph Manager that creates a Metadata Server (MDS) for the Ceph File System (CephFS). This section describes how to create a CephFS volume.

Note

This creates the Ceph File System, along with the data and metadata pools.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.

Procedure

  • Create a CephFS volume on the monitor node:

    Syntax

    ceph fs volume create VOLUME_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs volume create cephfs
    Copy to Clipboard Toggle word wrap

4.1.2. Listing Ceph file system volumes
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This section describes the step to list the Ceph File system (CephFS) volumes.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS volume.

Procedure

  • List the CephFS volume:

    Example

    [ceph: root@host01 /]# ceph fs volume ls
    Copy to Clipboard Toggle word wrap

You can list basic details about a Ceph File System (CephFS) volume, such as attributes of data and metadata pools of the CephFS volume, pending subvolumes deletion count, and the like.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS volume created.

Procedure

  • View information about a CephFS volume:

    Syntax

    ceph fs volume info VOLUME_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs volume info cephfs
{
    "mon_addrs": [
        "192.168.1.7:40977",
    ],
    "pending_subvolume_deletions": 0,
    "pools": {
        "data": [
            {
                "avail": 106288709632,
                "name": "cephfs.cephfs.data",
                "used": 4096
            }
        ],
        "metadata": [
            {
                "avail": 106288709632,
                "name": "cephfs.cephfs.meta",
                "used": 155648
            }
        ]
    },
    "used_size": 0
}
    Copy to Clipboard Toggle word wrap

The output of the ceph fs volume info command includes:

  • mon_addrs: List of monitor addresses.
  • pending_subvolume_deletions: Number of subvolumes pending deletion.

  • pools: Attributes of data and metadata pools.

    • avail: The amount of free space available in bytes.
    • name: Name of the pool.
    • used: The amount of storage consumed in bytes.
  • used_size: Current used size of the CephFS volume in bytes.

4.1.4. Removing a Ceph file system volume
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Ceph Orchestrator is a module for Ceph Manager that removes the Metadata Server (MDS) for the Ceph File System (CephFS). This section shows how to remove the Ceph File System (CephFS) volume.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS volume.

Procedure

  1. If the mon_allow_pool_delete option is not set to true, then set it to true before removing the CephFS volume:

    Example

    [ceph: root@host01 /]# ceph config set mon mon_allow_pool_delete true
    Copy to Clipboard Toggle word wrap

  2. Remove the CephFS volume:

    Syntax

    ceph fs volume rm VOLUME_NAME [--yes-i-really-mean-it]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs volume rm cephfs --yes-i-really-mean-it
    Copy to Clipboard Toggle word wrap

4.2. Ceph File System subvolume groups
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As a storage administrator, you can create, list, fetch absolute path, and remove Ceph File System (CephFS) subvolume groups. CephFS subvolume groups are abstractions at a directory level which effects policies, for example, file layouts, across a set of subvolumes.

Starting with Red Hat Ceph Storage 5.0, the subvolume group snapshot feature is not supported. You can only list and remove the existing snapshots of these subvolume groups.

This section describes how to:

4.2.1. Creating a file system subvolume group
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This section describes how to create a Ceph File System (CephFS) subvolume group.

Note

When creating a subvolume group, you can specify its data pool layout, uid, gid, and file mode in octal numerals. By default, the subvolume group is created with an octal file mode ‘755’, uid ‘0’, gid ‘0’, and data pool layout of its parent directory.

Note

See Setting and managing quotas on a file system subvolume group to set quotas while creating a subvolume group.

Prerequisites

  • A working Red Hat Ceph Storage cluster with a Ceph File System deployed.
  • At a minimum read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.

Procedure

  • Create a CephFS subvolume group:

    Syntax

    ceph fs subvolumegroup create VOLUME_NAME GROUP_NAME [--pool_layout DATA_POOL_NAME --uid UID --gid GID --mode OCTAL_MODE]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs subvolumegroup create cephfs subgroup0
    Copy to Clipboard Toggle word wrap

    The command succeeds even if the subvolume group already exists.

This section describes how to set and manage quotas on a Ceph File System (CephFS) subvolume group.

Prerequisites

  • A working Red Hat Ceph Storage cluster with a Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.

Procedure

  1. Set quotas while creating a subvolume group by providing size in bytes:

    Syntax

    ceph fs subvolumegroup create VOLUME_NAME GROUP_NAME [--size SIZE_IN_BYTES] [--pool_layout DATA_POOL_NAME] [--uid UID] [--gid GID] [--mode OCTAL_MODE]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs subvolumegroup create cephfs subvolgroup_2 10737418240
    Copy to Clipboard Toggle word wrap

  2. Resize a subvolume group:

    Syntax

    ceph fs subvolumegroup resize VOLUME_NAME GROUP_NAME new_size [--no_shrink]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs subvolumegroup resize cephfs subvolgroup_2 20737418240
[
    {
        "bytes_used": 10768679044
    },
    {
        "bytes_quota": 20737418240
    },
    {
        "bytes_pcent": "51.93"
    }
]
    Copy to Clipboard Toggle word wrap

  3. Fetch the metadata of a subvolume group:

    Syntax

    ceph fs subvolumegroup info VOLUME_NAME GROUP_NAME
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    Example

    [ceph: root@host01 /]# ceph fs subvolumegroup info cephfs subvolgroup_2
{
    "atime": "2022-10-05 18:00:39",
    "bytes_pcent": "51.85",
    "bytes_quota": 20768679043,
    "bytes_used": 10768679044,
    "created_at": "2022-10-05 18:00:39",
    "ctime": "2022-10-05 18:21:26",
    "data_pool": "cephfs.cephfs.data",
    "gid": 0,
    "mode": 16877,
    "mon_addrs": [
        "60.221.178.236:1221",
        "205.64.75.112:1221",
        "20.209.241.242:1221"
    ],
    "mtime": "2022-10-05 18:01:25",
    "uid": 0
}
    Copy to Clipboard Toggle word wrap

4.2.3. Listing file system subvolume groups
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This section describes the step to list the Ceph File System (CephFS) subvolume groups.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS subvolume group.

Procedure

  • List the CephFS subvolume groups:

    Syntax

    ceph fs subvolumegroup ls VOLUME_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs subvolumegroup ls cephfs
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This section shows how to fetch the absolute path of a Ceph File System (CephFS) subvolume group.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS subvolume group.

Procedure

  • Fetch the absolute path of the CephFS subvolume group:

    Syntax

    ceph fs subvolumegroup getpath VOLUME_NAME GROUP_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs subvolumegroup getpath cephfs subgroup0
    Copy to Clipboard Toggle word wrap

This section provides the steps to list the snapshots of a Ceph File System (CephFS) subvolume group.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS subvolume group.
  • Snapshots of the subvolume group.

Procedure

  • List the snapshots of a CephFS subvolume group:

    Syntax

    ceph fs subvolumegroup snapshot ls VOLUME_NAME GROUP_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs subvolumegroup snapshot ls cephfs subgroup0
    Copy to Clipboard Toggle word wrap

This section provides the step to remove snapshots of a Ceph File System (CephFS) subvolume group.

Note

Using the --force flag allows the command to succeed that would otherwise fail if the snapshot did not exist.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A Ceph File System volume.
  • A snapshot of the subvolume group.

Procedure

  • Remove the snapshot of the CephFS subvolume group:

    Syntax

    ceph fs subvolumegroup snapshot rm VOLUME_NAME GROUP_NAME SNAP_NAME [--force]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs subvolumegroup snapshot rm cephfs subgroup0 snap0 --force
    Copy to Clipboard Toggle word wrap

4.2.7. Removing a file system subvolume group
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This section shows how to remove the Ceph File System (CephFS) subvolume group.

Note

The removal of a subvolume group fails if it is not empty or non-existent. The --force flag allows the non-existent subvolume group to be removed.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS subvolume group.

Procedure

  • Remove the CephFS subvolume group:

    Syntax

    ceph fs subvolumegroup rm VOLUME_NAME GROUP_NAME [--force]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs subvolumegroup rm cephfs subgroup0 --force
    Copy to Clipboard Toggle word wrap

4.3. Ceph File System subvolumes
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As a storage administrator, you can create, list, fetch absolute path, fetch metadata, and remove Ceph File System (CephFS) subvolumes. Additionally, you can also create, list, and remove snapshots of these subvolumes. CephFS subvolumes are an abstraction for independent Ceph File Systems directory trees.

This section describes how to:

4.3.1. Creating a file system subvolume
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This section describes how to create a Ceph File System (CephFS) subvolume.

Note

When creating a subvolume, you can specify its subvolume group, data pool layout, uid, gid, file mode in octal numerals, and size in bytes. The subvolume can be created in a separate RADOS namespace by specifying the --namespace-isolated option. By default, a subvolume is created within the default subvolume group, and with an octal file mode ‘755’, uid of its subvolume group, gid of its subvolume group, data pool layout of its parent directory, and no size limit.

Prerequisites

  • A working Red Hat Ceph Storage cluster with a Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.

Procedure

  • Create a CephFS subvolume:

    Syntax

    ceph fs subvolume create VOLUME_NAME SUBVOLUME_NAME [--size SIZE_IN_BYTES --group_name SUBVOLUME_GROUP_NAME --pool_layout DATA_POOL_NAME --uid _UID --gid GID --mode OCTAL_MODE] [--namespace-isolated]
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph fs subvolume create cephfs sub0 --group_name subgroup0 --namespace-isolated
    Copy to Clipboard Toggle word wrap

    The command succeeds even if the subvolume already exists.

4.3.2. Listing file system subvolume
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This section describes the step to list the Ceph File System (CephFS) subvolume.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS subvolume.

Procedure

  • List the CephFS subvolume:

    Syntax

    ceph fs subvolume ls VOLUME_NAME [--group_name SUBVOLUME_GROUP_NAME]
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph fs subvolume ls cephfs --group_name subgroup0
    Copy to Clipboard Toggle word wrap

4.3.3. Resizing a file system subvolume
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This section describes the step to resize the Ceph File System (CephFS) subvolume.

Note

The ceph fs subvolume resize command resizes the subvolume quota using the size specified by new_size. The --no_shrink flag prevents the subvolume from shrinking below the currently used size of the subvolume. The subvolume can be resized to an infinite size by passing inf or infinite as the new_size.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS subvolume.

Procedure

  • Resize a CephFS subvolume:

    Syntax

    ceph fs subvolume resize VOLUME_NAME SUBVOLUME_NAME NEW_SIZE [--group_name SUBVOLUME_GROUP_NAME] [--no_shrink]
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph fs subvolume resize cephfs sub0 1024000000 --group_name subgroup0 --no_shrink
    Copy to Clipboard Toggle word wrap

This section shows how to fetch the absolute path of a Ceph File System (CephFS) subvolume.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS subvolume.

Procedure

  • Fetch the absolute path of the CephFS subvolume:

    Syntax

    ceph fs subvolume getpath VOLUME_NAME SUBVOLUME_NAME [--group_name _SUBVOLUME_GROUP_NAME]
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph fs subvolume getpath cephfs sub0 --group_name subgroup0
    Copy to Clipboard Toggle word wrap

This section shows how to fetch metadata of a Ceph File System (CephFS) subvolume.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS subvolume.

Procedure

  • Fetch the metadata of a CephFS subvolume:

    Syntax

    ceph fs subvolume info VOLUME_NAME SUBVOLUME_NAME [--group_name SUBVOLUME_GROUP_NAME]
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph fs subvolume info cephfs sub0 --group_name subgroup0
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    Example output

    # ceph fs subvolume info cephfs sub0
{
    "atime": "2023-07-14 08:52:46",
    "bytes_pcent": "0.00",
    "bytes_quota": 1024000000,
    "bytes_used": 0,
    "created_at": "2023-07-14 08:52:46",
    "ctime": "2023-07-14 08:53:54",
    "data_pool": "cephfs.cephfs.data",
    "features": [
        "snapshot-clone",
        "snapshot-autoprotect",
        "snapshot-retention"
    ],
    "flavor": "2",
    "gid": 0,
    "mode": 16877,
    "mon_addrs": [
        "10.0.208.172:6789",
        "10.0.211.197:6789",
        "10.0.209.212:6789"
    ],
    "mtime": "2023-07-14 08:52:46",
    "path": "/volumes/_nogroup/sub0/834c5cbc-f5db-4481-80a3-aca92ff0e7f3",
    "pool_namespace": "",
    "state": "complete",
    "type": "subvolume",
    "uid": 0
}
    Copy to Clipboard Toggle word wrap

The output format is JSON and contains the following fields:

  • atime: access time of subvolume path in the format "YYYY-MM-DD HH:MM:SS".
  • bytes_pcent: quota used in percentage if quota is set, else displays "undefined".
  • bytes_quota: quota size in bytes if quota is set, else displays "infinite".
  • bytes_used: current used size of the subvolume in bytes.
  • created_at: time of creation of subvolume in the format "YYYY-MM-DD HH:MM:SS".
  • ctime: change time of subvolume path in the format "YYYY-MM-DD HH:MM:SS".
  • data_pool: data pool the subvolume belongs to.
  • features: features supported by the subvolume, such as , "snapshot-clone", "snapshot-autoprotect", or "snapshot-retention".
  • flavor: subvolume version, either 1 for version one or 2 for version two.
  • gid: group ID of subvolume path.
  • mode: mode of subvolume path.
  • mon_addrs: list of monitor addresses.
  • mtime: modification time of subvolume path in the format "YYYY-MM-DD HH:MM:SS".
  • path: absolute path of a subvolume.
  • pool_namespace: RADOS namespace of the subvolume.
  • state: current state of the subvolume, such as, "complete" or "snapshot-retained".
  • type: subvolume type indicating whether it is a clone or subvolume.
  • uid: user ID of subvolume path.

This section shows how to create snapshots of a Ceph File System (CephFS) subvolume.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS subvolume.
  • In addition to read (r) and write (w) capabilities, clients also require s flag on a directory path within the file system.

Procedure

  1. Verify that the s flag is set on the directory:

    Syntax

    ceph auth get CLIENT_NAME
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    Example

    [root@mon ~]# ceph auth get client.0
[client.0]
    key = AQAz7EVWygILFRAAdIcuJ12opU/JKyfFmxhuaw==
    caps mds = "allow rw, allow rws path=/bar"
    1 
    
    caps mon = "allow r"
    caps osd = "allow rw tag cephfs data=cephfs_a"
    2
    Copy to Clipboard Toggle word wrap

    1 2
    In the example, client.0 can create or delete snapshots in the bar directory of file system cephfs_a.

  2. Create a snapshot of the Ceph File System subvolume:

    Syntax

    ceph fs subvolume snapshot create VOLUME_NAME SUBVOLUME_NAME SNAP_NAME [--group_name GROUP_NAME]
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph fs subvolume snapshot create cephfs sub0 snap0 --group_name subgroup0
    Copy to Clipboard Toggle word wrap

4.3.7. Cloning subvolumes from snapshots
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Subvolumes can be created by cloning subvolume snapshots. It is an asynchronous operation involving copying data from a snapshot to a subvolume.

Note

Cloning is inefficient for very large data sets.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.

  • To create or delete snapshots, in addition to read and write capability, clients require s flag on a directory path within the filesystem.

    Syntax

    CLIENT_NAME
    key = AQAz7EVWygILFRAAdIcuJ12opU/JKyfFmxhuaw==
    caps mds = allow rw, allow rws path=DIRECTORY_PATH
    caps mon = allow r
    caps osd = allow rw tag cephfs data=DIRECTORY_NAME
    Copy to Clipboard Toggle word wrap

    In the following example, client.0 can create or delete snapshots in the bar directory of filesystem cephfs_a.

    Example

    [client.0]
    key = AQAz7EVWygILFRAAdIcuJ12opU/JKyfFmxhuaw==
    caps mds = "allow rw, allow rws path=/bar"
    caps mon = "allow r"
    caps osd = "allow rw tag cephfs data=cephfs_a"
    Copy to Clipboard Toggle word wrap

Procedure

  1. Create a Ceph File System (CephFS) volume:

    Syntax

    ceph fs volume create VOLUME_NAME
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    Example

    [root@mon ~]# ceph fs volume create cephfs
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    This creates the CephFS file system, its data and metadata pools.

  2. Create a subvolume group. By default, the subvolume group is created with an octal file mode '755', and data pool layout of its parent directory.

    Syntax

    ceph fs subvolumegroup create VOLUME_NAME GROUP_NAME [--pool_layout DATA_POOL_NAME --uid UID --gid GID --mode OCTAL_MODE]
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    Example

    [root@mon ~]# ceph fs subvolumegroup create cephfs subgroup0
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  3. Create a subvolume. By default, a subvolume is created within the default subvolume group, and with an octal file mode ‘755’, uid of its subvolume group, gid of its subvolume group, data pool layout of its parent directory, and no size limit.

    Syntax

    ceph fs subvolume create VOLUME_NAME SUBVOLUME_NAME [--size SIZE_IN_BYTES --group_name SUBVOLUME_GROUP_NAME --pool_layout DATA_POOL_NAME --uid _UID --gid GID --mode OCTAL_MODE]
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph fs subvolume create cephfs sub0 --group_name subgroup0
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  4. Create a snapshot of a subvolume:

    Syntax

    ceph fs subvolume snapshot create VOLUME_NAME _SUBVOLUME_NAME SNAP_NAME [--group_name SUBVOLUME_GROUP_NAME]
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph fs subvolume snapshot create cephfs sub0 snap0  --group_name subgroup0
    Copy to Clipboard Toggle word wrap

  5. Initiate a clone operation:

    Note

    By default, cloned subvolumes are created in the default group.

    1. If the source subvolume and the target clone are in the default group, run the following command:

      Syntax

      ceph fs subvolume snapshot clone VOLUME_NAME SUBVOLUME_NAME SNAP_NAME TARGET_CLONE_NAME
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      Example

      [root@mon ~]# ceph fs subvolume snapshot clone cephfs sub0 snap0 clone0
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    2. If the source subvolume is in the non-default group, then specify the source subvolume group in the following command:

      Syntax

      ceph fs subvolume snapshot clone VOLUME_NAME SUBVOLUME_NAME SNAP_NAME TARGET_CLONE_NAME --group_name SUBVOLUME_GROUP_NAME
      Copy to Clipboard Toggle word wrap

      Example

      [root@mon ~]# ceph fs subvolume snapshot clone cephfs sub0 snap0 clone0 --group_name subgroup0
      Copy to Clipboard Toggle word wrap

    3. If the target clone is to a non-default group, then specify the target group in the following command:

      Syntax

      ceph fs subvolume snapshot clone VOLUME_NAME SUBVOLUME_NAME SNAP_NAME TARGET_CLONE_NAME --target_group_name SUBVOLUME_GROUP_NAME
      Copy to Clipboard Toggle word wrap

      Example

      [root@mon ~]# ceph fs subvolume snapshot clone cephfs sub0 snap0 clone0 --target_group_name subgroup1
      Copy to Clipboard Toggle word wrap

  6. Check the status of the clone operation:

    Syntax

    ceph fs clone status VOLUME_NAME CLONE_NAME [--group_name TARGET_GROUP_NAME]
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    Example

    [root@mon ~]# ceph fs clone status cephfs clone0 --group_name subgroup1

{
  "status": {
    "state": "complete"
  }
}
    Copy to Clipboard Toggle word wrap

Additional Resources

This section provides the step to list the snapshots of a Ceph File system (CephFS) subvolume.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS subvolume.
  • Snapshots of the subvolume.

Procedure

  • List the snapshots of a CephFS subvolume:

    Syntax

    ceph fs subvolume snapshot ls VOLUME_NAME SUBVOLUME_NAME [--group_name SUBVOLUME_GROUP_NAME]
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph fs subvolume snapshot ls cephfs sub0 --group_name subgroup0
    Copy to Clipboard Toggle word wrap

This section provides the step to fetch the metadata of the snapshots of a Ceph File System (CephFS) subvolume.

Prerequisites

  • A working Red Hat Ceph Storage cluster with CephFS deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS subvolume.
  • Snapshots of the subvolume.

Procedure

  1. Fetch the metadata of the snapshots of a CephFS subvolume:

    Syntax

    ceph fs subvolume snapshot info VOLUME_NAME SUBVOLUME_NAME SNAP_NAME [--group_name SUBVOLUME_GROUP_NAME]
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph fs subvolume snapshot info cephfs sub0 snap0 --group_name subgroup0
    Copy to Clipboard Toggle word wrap

    Example output

    {
    "created_at": "2022-05-09 06:18:47.330682",
    "data_pool": "cephfs_data",
    "has_pending_clones": "no",
    "size": 0
}
    Copy to Clipboard Toggle word wrap

The output format is JSON and contains the following fields:

  • created_at: time of creation of snapshot in the format "YYYY-MM-DD HH:MM:SS:ffffff".
  • data_pool: data pool the snapshot belongs to.
  • has_pending_clones: "yes" if snapshot clone is in progress otherwise "no".
  • size: snapshot size in bytes.

4.3.10. Removing a file system subvolume
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This section describes the step to remove the Ceph File System (CephFS) subvolume.

Note

The ceph fs subvolume rm command removes the subvolume and its contents in two steps. First, it moves the subvolume to a trash folder, and then asynchronously purges its contents.

A subvolume can be removed retaining existing snapshots of the subvolume using the --retain-snapshots option. If snapshots are retained, the subvolume is considered empty for all operations not involving the retained snapshots. Retained snapshots can be used as a clone source to recreate the subvolume, or cloned to a newer subvolume.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS subvolume.

Procedure

  1. Remove a CephFS subvolume:

    Syntax

    ceph fs subvolume rm VOLUME_NAME SUBVOLUME_NAME [--group_name SUBVOLUME_GROUP_NAME] [--force] [--retain-snapshots]
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    Example

    [root@mon ~]# ceph fs subvolume rm cephfs sub0 --group_name subgroup0 --retain-snapshots
    Copy to Clipboard Toggle word wrap

  2. To recreate a subvolume from a retained snapshot:

    Syntax

    ceph fs subvolume snapshot clone VOLUME_NAME DELETED_SUBVOLUME RETAINED_SNAPSHOT NEW_SUBVOLUME --group_name SUBVOLUME_GROUP_NAME --target_group_name SUBVOLUME_TARGET_GROUP_NAME
    Copy to Clipboard Toggle word wrap

    • NEW_SUBVOLUME can either be the same subvolume which was deleted earlier or clone it to a new subvolume.

    Example

    [root@mon ~]# ceph fs subvolume snapshot clone cephfs sub0 snap0 sub1 --group_name subgroup0 --target_group_name subgroup0
    Copy to Clipboard Toggle word wrap

This section provides the step to remove snapshots of a Ceph File System (CephFS) subvolume group.

Note

Using the --force flag allows the command to succeed that would otherwise fail if the snapshot did not exist.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A Ceph File System volume.
  • A snapshot of the subvolume group.

Procedure

  • Remove the snapshot of the CephFS subvolume:

    Syntax

    ceph fs subvolume snapshot rm VOLUME_NAME SUBVOLUME_NAME SNAP_NAME [--group_name GROUP_NAME --force]
    Copy to Clipboard Toggle word wrap

    Example

    [root@mon ~]# ceph fs subvolume snapshot rm cephfs sub0 snap0 --group_name subgroup0 --force
    Copy to Clipboard Toggle word wrap

As a storage administrator, you can set, get, list, and remove metadata information of Ceph File System (CephFS) subvolumes.

The custom metadata is for users to store their metadata in subvolumes. Users can store the key-value pairs similar to xattr in a Ceph File System.

This section describes how to:

You can set custom metadata on the file system subvolume as a key-value pair.

Note

If the key_name already exists then the old value is replaced by the new value.

Note

The KEY_NAME and VALUE should be a string of ASCII characters as specified in python’s string.printable. The KEY_NAME is case-insensitive and is always stored in lower case.

Important

Custom metadata on a subvolume is not preserved when snapshotting the subvolume, and hence, is also not preserved when cloning the subvolume snapshot.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • A Ceph File System (CephFS), CephFS volume, subvolume group, and subvolume created.

Procedure

  1. Set the metadata on the CephFS subvolume:

    Syntax

    ceph fs subvolume metadata set VOLUME_NAME SUBVOLUME_NAME KEY_NAME VALUE [--group_name SUBVOLUME_GROUP_NAME]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs subvolume metadata set cephfs sub0 test_meta cluster --group_name subgroup0
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  2. Optional: Set the custom metadata with a space in the KEY_NAME:

    Example

    [ceph: root@host01 /]# ceph fs subvolume metadata set cephfs sub0 "test meta" cluster --group_name subgroup0
    Copy to Clipboard Toggle word wrap

    This creates another metadata with KEY_NAME as test meta for the VALUE cluster.

  3. Optional: You can also set the same metadata with a different value:

    Example

    [ceph: root@host01 /]# ceph fs subvolume metadata set cephfs sub0 "test_meta" cluster2 --group_name subgroup0
    Copy to Clipboard Toggle word wrap

You can get the custom metadata, the key-value pairs, of a Ceph File System (CephFS) in a volume, and optionally, in a specific subvolume group.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • A CephFS volume, subvolume group, and subvolume created.
  • A custom metadata created on the CephFS subvolume.

Procedure

  • Get the metadata on the CephFS subvolume:

    Syntax

    ceph fs subvolume metadata get VOLUME_NAME SUBVOLUME_NAME KEY_NAME [--group_name SUBVOLUME_GROUP_NAME]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs subvolume metadata get cephfs sub0 test_meta --group_name subgroup0

cluster
    Copy to Clipboard Toggle word wrap

You can list the custom metadata associated with the key of a Ceph File System (CephFS) in a volume, and optionally, in a specific subvolume group.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • A CephFS volume, subvolume group, and subvolume created.
  • A custom metadata created on the CephFS subvolume.

Procedure

  • List the metadata on the CephFS subvolume:

    Syntax

    ceph fs subvolume metadata ls VOLUME_NAME SUBVOLUME_NAME [--group_name SUBVOLUME_GROUP_NAME]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs subvolume metadata ls cephfs sub0
{
    "test_meta": "cluster"
}
    Copy to Clipboard Toggle word wrap

You can remove the custom metadata, the key-value pairs, of a Ceph File System (CephFS) in a volume, and optionally, in a specific subvolume group.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • A CephFS volume, subvolume group, and subvolume created.
  • A custom metadata created on the CephFS subvolume.

Procedure

  1. Remove the custom metadata on the CephFS subvolume:

    Syntax

    ceph fs subvolume metadata rm VOLUME_NAME SUBVOLUME_NAME KEY_NAME [--group_name SUBVOLUME_GROUP_NAME]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs subvolume metadata rm cephfs sub0 test_meta --group_name subgroup0
    Copy to Clipboard Toggle word wrap

  2. List the metadata:

    Example

    [ceph: root@host01 /]# ceph fs subvolume metadata ls cephfs sub0

{}
    Copy to Clipboard Toggle word wrap

Chapter 5. Ceph File System administration
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As a storage administrator, you can perform common Ceph File System (CephFS) administrative tasks, such as:

Prerequisites

  • A running, and healthy Red Hat Ceph Storage cluster.
  • Installation and configuration of the Ceph Metadata Server daemons (ceph-mds).
  • Create and mount a Ceph File System.

5.1. Using the cephfs-top utility
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The Ceph File System (CephFS) provides a top-like utility to display metrics on Ceph File Systems in realtime. The cephfs-top utility is a curses-based Python script that uses the Ceph Manager stats module to fetch and display client performance metrics.

Currently, the cephfs-top utility supports nearly 10k clients.

Note

Currently, not all of the performance stats are available in the Red Hat Enterprise Linux 9.2 kernel. cephfs-top is supported on Red Hat Enterprise Linux 9 and above and uses one of the standard terminals in Red Hat Enterprise Linux.

Important

The minimum compatible python version for cephfs-top utility is 3.6.0.

Prerequisites

  • A healthy and running Red Hat Ceph Storage cluster.
  • Deployment of a Ceph File System.
  • Root-level access to a Ceph client node.
  • Installation of the cephfs-top package.

Procedure

  1. Enable the Red Hat Ceph Storage 7 tools repository, if it is not already enabled:

    Red Hat Enterprise Linux 9

    [root@client ~]# subscription-manager repos --enable=rhceph-7-tools-for-rhel-9-x86_64-rpms
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  2. Install the cephfs-top package:

    Example

    [root@client ~]# dnf install cephfs-top
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  3. Enable the Ceph Manager stats plugin:

    Example

    [root@client ~]# ceph mgr module enable stats
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  4. Create the client.fstop Ceph user:

    Example

    [root@client ~]# ceph auth get-or-create client.fstop mon 'allow r' mds 'allow r' osd 'allow r' mgr 'allow r' > /etc/ceph/ceph.client.fstop.keyring
    Copy to Clipboard Toggle word wrap

    Note

    Optionally, use the --id argument to specify a different Ceph user, other than client.fstop.

  5. Start the cephfs-top utility:

    Example

    [root@client ~]# cephfs-top
cephfs-top - Wed Nov 30 15:26:05 2022

All Filesystem Info
Total Client(s): 4 - 3 FUSE, 1 kclient, 0 libcephfs
COMMANDS: m - select a filesystem | s - sort menu | l - limit number of clients | r - reset to default | q - quit

  client_id mount_root chit(%) dlease(%) ofiles oicaps oinodes rtio(MB) raio(MB) rsp(MB/s) wtio(MB) waio(MB) wsp(MB/s) rlatavg(ms) rlatsd(ms) wlatavg(ms) wlatsd(ms) mlatavg(ms) mlatsd(ms) mount_point@host/addr

Filesystem: cephfs1 - 2 client(s)


  4500     /          100.0   100.0	     0	    751    0       0.0	    0.0	     0.0	   578.13   0.03     0.0       N/A         N/A        N/A         N/A       N/A        N/A       N/A@example/192.168.1.4
  4501     /          100.0   0.0      0	    1    0       0.0	    0.0	     0.0	   0.0   0.0     0.0       0.0         0.0        0.0         0.0        0.41        0.0       /mnt/cephfs2@example/192.168.1.4

Filesystem: cephfs2 - 2 client(s)


  4512     /          100.0   0.0	     0	    1      0       0.0	    0.0	     0.0	   0.0      0.0      0.0       0.0         0.0        0.0         0.0        0.4        0.0        /mnt/cephfs3@example/192.168.1.4
  4518     /          100.0   0.0	     0	    1      0       0.0	    0.0	     0.0	   0.0      0.0      0.0       0.0         0.0        0.0         0.0        0.52        0.0        /mnt/cephfs4@example/192.168.1.4
    Copy to Clipboard Toggle word wrap

5.1.1. The cephfs-top utility interactive commands
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Select a particular file system and view the metrics related to that file system with the cephfs-top utility interactive commands.

m
Description
Filesystem selection: Displays a menu of file systems for selection.
q
Description
Quit: Exits the utility if you are at the home screen with all file system information. If you are not at the home screen, it redirects you back to the home screen.
s
Description
Sort field selection: Designates the sort field. ‘cap_hit’ is the default.
l
Description
Client limit: Sets the limit on the number of clients to be displayed.
r
Description
Reset: Resets the sort field and limit value to the default.

The metrics display can be scrolled using the Arrow Keys, PgUp/PgDn, Home/End and mouse.

Example of entering and exiting the file system selection menu

[root@client ~]# m

                       Filesystems
Press "q" to go back to home (all filesystem info) screen



                        cephfs01
                        cephfs02
[root@client ~]# q

cephfs-top - Thu Oct 20 07:29:35 2022
Total Client(s): 3 - 2 FUSE, 1 kclient, 0 libcephfs
Copy to Clipboard Toggle word wrap

5.1.2. The cephfs-top utility options
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You can use the cephfs-top utility command with various options.

Example

[root@client ~]# cephfs-top --selftest
selftest ok
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--cluster NAME_OF_THE_CLUSTER
Description
With this option, you can connect to the non-default cluster name. The default name is ceph.
--id USER
Description
This is a client which connects to the Ceph cluster and is fstop by default.
--selftest
Description
With this option, you can perform a selftest. This mode performs a sanity check of stats module.
--conffile PATH_TO_THE_CONFIGURATION_FILE
Description
With this option, you can provide a path to the Ceph cluster configuration file.
-d/--delay INTERVAL_IN_SECONDS
Description

The cephfs-top utility refreshes statistics every second by default. With this option, you can change a refresh interval.

Note

Interval should be greater than or equal to 1 seconds. Fractional seconds are honored.

--dump
Description
With this option, you can dump the metrics to stdout without creating a curses display use.
--dumpfs FILE_SYSTEM_NAME
Description
With this option, you can dump the metrics of the given filesystem to stdout without creating a curses display use.

5.2. Using the MDS autoscaler module
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The MDS Autoscaler Module monitors the Ceph File System (CephFS) to ensure sufficient MDS daemons are available. It works by adjusting the placement specification for the Orchestrator backend of the MDS service.

The module monitors the following file system settings to inform placement count adjustments:

  • max_mds file system setting
  • standby_count_wanted file system setting

The Ceph monitor daemons are still responsible for promoting or stopping MDS according to these settings. The mds_autoscaler simply adjusts the number of MDS which are spawned by the orchestrator.

Prerequisites

  • A healthy and running Red Hat Ceph Storage cluster.
  • Deployment of a Ceph File System.
  • Root-level access to a Ceph Monitor node.

Procedure

  • Enable the MDS autoscaler module:

    Example

    [ceph: root@host01 /]# ceph mgr module enable mds_autoscaler
    Copy to Clipboard Toggle word wrap

How to unmount a Ceph File System that is mounted as a kernel client.

Prerequisites

  • Root-level access to the node doing the mounting.

Procedure

  • To unmount a Ceph File System mounted as a kernel client:

    Syntax

    umount MOUNT_POINT
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    Example

    [root@client ~]# umount /mnt/cephfs
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Additional Resources

  • The umount(8) manual page

Unmounting a Ceph File System that is mounted as a File System in User Space (FUSE) client.

Prerequisites

  • Root-level access to the FUSE client node.

Procedure

  • To unmount a Ceph File System mounted in FUSE:

    Syntax

    fusermount -u MOUNT_POINT
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    Example

    [root@client ~]# fusermount -u /mnt/cephfs
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Additional Resources

  • The ceph-fuse(8) manual page

You can map a directory and its subdirectories to a particular active Metadata Server (MDS) rank so that its metadata is only managed by the MDS daemon holding that rank. This approach enables you to evenly spread application load or the limit impact of users' metadata requests to the entire storage cluster.

Important

An internal balancer already dynamically spreads the application load. Therefore, only map directory trees to ranks for certain carefully chosen applications.

In addition, when a directory is mapped to a rank, the balancer cannot split it. Consequently, a large number of operations within the mapped directory can overload the rank and the MDS daemon that manages it.

Prerequisites

  • At least two active MDS daemons.
  • User access to the CephFS client node.
  • Verify that the attr package is installed on the CephFS client node with a mounted Ceph File System.

Procedure

  1. Add the p flag to the Ceph user’s capabilities:

    Syntax

    ceph fs authorize FILE_SYSTEM_NAME client.CLIENT_NAME /DIRECTORY CAPABILITY [/DIRECTORY CAPABILITY] ...
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    Example

    [user@client ~]$ ceph fs authorize cephfs_a client.1 /temp rwp

client.1
  key: AQBSdFhcGZFUDRAAcKhG9Cl2HPiDMMRv4DC43A==
  caps: [mds] allow r, allow rwp path=/temp
  caps: [mon] allow r
  caps: [osd] allow rw tag cephfs data=cephfs_a
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  2. Set the ceph.dir.pin extended attribute on a directory:

    Syntax

    setfattr -n ceph.dir.pin -v RANK DIRECTORY
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    Example

    [user@client ~]$ setfattr -n ceph.dir.pin -v 2 /temp
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    This example assigns the /temp directory and all of its subdirectories to rank 2.

Additional Resources

Disassociate a directory from a particular active Metadata Server (MDS) rank.

Prerequisites

  • User access to the Ceph File System (CephFS) client node.
  • Ensure that the attr package is installed on the client node with a mounted CephFS.

Procedure

  • Set the ceph.dir.pin extended attribute to -1 on a directory:

    Syntax

    setfattr -n ceph.dir.pin -v -1 DIRECTORY
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    Example

    [user@client ~]$ setfattr -n ceph.dir.pin -v -1 /home/ceph-user
    Copy to Clipboard Toggle word wrap

    Note

    Any separately mapped subdirectories of /home/ceph-user/ are not affected.

Additional Resources

5.7. Adding data pools
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The Ceph File System (CephFS) supports adding more than one pool to be used for storing data. This can be useful for:

  • Storing log data on reduced redundancy pools.
  • Storing user home directories on an SSD or NVMe pool.
  • Basic data segregation.

Before using another data pool in the Ceph File System, you must add it as described in this section.

By default, for storing file data, CephFS uses the initial data pool that was specified during its creation. To use a secondary data pool, you must also configure a part of the file system hierarchy to store file data in that pool or optionally within a namespace of that pool, using file and directory layouts.

Prerequisites

  • Root-level access to the Ceph Monitor node.

Procedure

  1. Create a new data pool:

    Syntax

    ceph osd pool create POOL_NAME
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    Replace:

    • POOL_NAME with the name of the pool.

    Example

    [ceph: root@host01 /]# ceph osd pool create cephfs_data_ssd

pool 'cephfs_data_ssd' created
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  2. Add the newly created pool under the control of the Metadata Servers:

    Syntax

    ceph fs add_data_pool FS_NAME POOL_NAME
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    Replace:

    • FS_NAME with the name of the file system.
    • POOL_NAME with the name of the pool.

    Example:

    [ceph: root@host01 /]# ceph fs add_data_pool cephfs cephfs_data_ssd

added data pool 6 to fsmap
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  3. Verify that the pool was successfully added:

    Example

    [ceph: root@host01 /]# ceph fs ls

name: cephfs, metadata pool: cephfs_metadata, data pools: [cephfs_data cephfs_data_ssd]
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  4. Optional: Remove a data pool from the file system:

    Syntax

    ceph fs rm_data_pool FS_NAME POOL_NAME
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    Example:

    [ceph: root@host01 /]# ceph fs rm_data_pool cephfs cephfs_data_ssd

removed data pool 6 from fsmap
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    1. Verify that the pool was successfully removed:

      Example

      [ceph: root@host01 /]# ceph fs ls

name: cephfs, metadata pool: cephfs_metadata, data pools: [cephfs.cephfs.data]
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  5. If you use the cephx authentication, make sure that clients can access the new pool.

Additional Resources

5.8. Taking down a Ceph File System cluster
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You can take down Ceph File System (CephFS) cluster by setting the down flag to true. Doing this gracefully shuts down the Metadata Server (MDS) daemons by flushing journals to the metadata pool and stopping all client I/O.

You can also take the CephFS cluster down quickly to test the deletion of a file system and bring the Metadata Server (MDS) daemons down, for example, when practicing a disaster recovery scenario. Doing this sets the jointable flag to prevent the MDS standby daemons from activating the file system.

Prerequisites

  • Root-level access to a Ceph Monitor node.

Procedure

  1. To mark the CephFS cluster down:

    Syntax

    ceph fs set FS_NAME down true
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    Example

    [ceph: root@host01 /]# ceph fs set cephfs down true
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    1. To bring the CephFS cluster back up:

      Syntax

      ceph fs set FS_NAME down false
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      Example

      [ceph: root@host01 /]# ceph fs set cephfs down false
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    or

  1. To quickly take down a CephFS cluster:

    Syntax

    ceph fs fail FS_NAME
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    Example

    [ceph: root@host01 /]# ceph fs fail cephfs
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    Note

    To get the CephFS cluster back up, set cephfs to joinable:

    Syntax

    ceph fs set FS_NAME joinable true
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    Example

    [ceph: root@host01 /]# ceph fs set cephfs joinable true

cephfs marked joinable; MDS may join as newly active.
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5.9. Removing a Ceph File System
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You can remove a Ceph File System (CephFS). Before doing so, consider backing up all the data and verifying that all clients have unmounted the file system locally.

Warning

This operation is destructive and will make the data stored on the Ceph File System permanently inaccessible.

Prerequisites

  • Back up your data.
  • Root-level access to a Ceph Monitor node.

Procedure

  1. Mark the storage cluster as down:

    Syntax

    ceph fs set FS_NAME down true
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    Replace
    • FS_NAME with the name of the Ceph File System you want to remove.

    Example

    [ceph: root@host01 /]# ceph fs set cephfs down true

cephfs marked down.
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  2. Display the status of the Ceph File System: 

    ceph fs status
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    Example

    [ceph: root@host01 /]# ceph fs status

cephfs - 0 clients
======
+-------------------+----------+-------+-------+
|       POOL        |   TYPE   |  USED | AVAIL |
+-----------------+------------+-------+-------+
|cephfs.cephfs.meta | metadata | 31.5M |  52.6G|
|cephfs.cephfs.data |   data   |    0  |  52.6G|
+-----------------+----------+-------+---------+
               STANDBY MDS
cephfs.ceph-host01
cephfs.ceph-host02
cephfs.ceph-host03
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  3. Remove the Ceph File System:

    Syntax

    ceph fs rm FS_NAME --yes-i-really-mean-it
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    Replace
    • FS_NAME with the name of the Ceph File System you want to remove.

    Example

    [ceph: root@host01 /]# ceph fs rm cephfs --yes-i-really-mean-it
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  4. Verify that the file system has been successfully removed:

    Example

    [ceph: root@host01 /]# ceph fs ls
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  5. Optional. Remove data and metadata pools associated with the removed file system.

Additional Resources

  • See the Delete a Pool section in the Red Hat Ceph Storage Storage Strategies Guide.

5.10. Using the ceph mds fail command
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Use the ceph mds fail command to:

  • Mark a MDS daemon as failed. If the daemon was active and a suitable standby daemon was available, and if the standby daemon was active after disabling the standby-replay configuration, using this command forces a failover to the standby daemon. By disabling the standby-replay daemon, this prevents new standby-replay daemons from being assigned.
  • Restart a running MDS daemon. If the daemon was active and a suitable standby daemon was available, the "failed" daemon becomes a standby daemon.

Prerequisites

  • Installation and configuration of the Ceph MDS daemons.

Procedure

  • To fail a daemon:

    Syntax

    ceph mds fail MDS_NAME
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    Where MDS_NAME is the name of the standby-replay MDS node.

    Example

    [ceph: root@host01 /]# ceph mds fail example01
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    Note

    You can find the Ceph MDS name from the ceph fs status command.

5.11. Client features
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At times you might want to set Ceph File System (CephFS) features that clients must support to enable them to use Ceph File Systems. Clients without these features might disrupt other CephFS clients, or behave in unexpected ways. Also, you might want to require new features to prevent older, and possibly buggy clients from connecting to a Ceph File System.

Important

CephFS clients missing newly added features are evicted automatically.

You can list all the CephFS features by using the fs features ls command. You can add or remove requirements by using the fs required_client_features command.

Syntax

fs required_client_features FILE_SYSTEM_NAME add FEATURE_NAME
fs required_client_features FILE_SYSTEM_NAME rm FEATURE_NAME
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Feature Descriptions

reply_encoding
Description
The Ceph Metadata Server (MDS) encodes reply requests in extensible format, if the client supports this feature.
reclaim_client
Description
The Ceph MDS allows a new client to reclaim another, perhaps a dead, client’s state. This feature is used by NFS Ganesha.
lazy_caps_wanted
Description
When a stale client resumes, the Ceph MDS only needs to re-issue the capabilities that are explicitly wanted, if the client supports this feature.
multi_reconnect
Description
After a Ceph MDS failover event, the client sends a reconnect message to the MDS to reestablish cache states. A client can split large reconnect messages into multiple messages.
deleg_ino
Description
A Ceph MDS delegates inode numbers to a client, if the client supports this feature. Delegating inode numbers is a prerequisite for a client to do async file creation.
metric_collect
Description
CephFS clients can send performance metrics to a Ceph MDS.
alternate_name
Description
CephFS clients can set and understand alternate names for directory entries. This feature allows for encrypted file names.

5.12. Ceph File System client evictions
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When a Ceph File System (CephFS) client is unresponsive or misbehaving, it might be necessary to forcibly terminate, or evict it from accessing the CephFS. Evicting a CephFS client prevents it from communicating further with Metadata Server (MDS) daemons and Ceph OSD daemons. If a CephFS client is buffering I/O to the CephFS at the time of eviction, then any un-flushed data will be lost. The CephFS client eviction process applies to all client types: FUSE mounts, kernel mounts, NFS gateways, and any process using libcephfs API library.

You can evict CephFS clients automatically, if they fail to communicate promptly with the MDS daemon, or manually.

Automatic Client Eviction

These scenarios cause an automatic CephFS client eviction:

  • If a CephFS client has not communicated with the active MDS daemon for over the default of 300 seconds, or as set by the session_autoclose option.
  • If the mds_cap_revoke_eviction_timeout option is set, and a CephFS client has not responded to the cap revoke messages for over the set amount of seconds. The mds_cap_revoke_eviction_timeout option is disabled by default.
  • During MDS startup or failover, the MDS daemon goes through a reconnect phase waiting for all the CephFS clients to connect to the new MDS daemon. If any CephFS clients fail to reconnect within the default time window of 45 seconds, or as set by the mds_reconnect_timeout option.

5.13. Blocklist Ceph File System clients
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Ceph File System (CephFS) client blocklisting is enabled by default. When you send an eviction command to a single Metadata Server (MDS) daemon, it propagates the blocklist to the other MDS daemons. This is to prevent the CephFS client from accessing any data objects, so it is necessary to update the other CephFS clients, and MDS daemons with the latest Ceph OSD map, which includes the blocklisted client entries.

An internal “osdmap epoch barrier” mechanism is used when updating the Ceph OSD map. The purpose of the barrier is to verify the CephFS clients receiving the capabilities have a sufficiently recent Ceph OSD map, before any capabilities are assigned that might allow access to the same RADOS objects, as to not race with canceled operations, such as, from ENOSPC or blocklisted clients from evictions.

If you are experiencing frequent CephFS client evictions due to slow nodes or an unreliable network, and you cannot fix the underlying issue, then you can ask the MDS to be less strict. It is possible to respond to slow CephFS clients by simply dropping their MDS sessions, but permit the CephFS client to re-open sessions and to continue talking to Ceph OSDs. By setting the mds_session_blocklist_on_timeout and mds_session_blocklist_on_evict options to false enables this mode.

Note

When blocklisting is disabled, the evicted CephFS client has only an effect on the MDS daemon you send the command to. On a system with multiple active MDS daemons, you need to send an eviction command to each active daemon.

5.14. Manually evicting a Ceph File System client
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You might want to manually evict a Ceph File System (CephFS) client, if the client is misbehaving and you do not have access to the client node, or if a client dies, and you do not want to wait for the client session to time out.

Prerequisites

  • Root-level access to the Ceph Monitor node.

Procedure

  1. Review the client list:

    Syntax

    ceph tell DAEMON_NAME client ls
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    Example

    [ceph: root@host01 /]# ceph tell mds.0 client ls
[
    {
        "id": 4305,
        "num_leases": 0,
        "num_caps": 3,
        "state": "open",
        "replay_requests": 0,
        "completed_requests": 0,
        "reconnecting": false,
        "inst": "client.4305 172.21.9.34:0/422650892",
        "client_metadata": {
            "ceph_sha1": "79f0367338897c8c6d9805eb8c9ad24af0dcd9c7",
            "ceph_version": "ceph version 16.2.8-65.el8cp (79f0367338897c8c6d9805eb8c9ad24af0dcd9c7)",
            "entity_id": "0",
            "hostname": "senta04",
            "mount_point": "/tmp/tmpcMpF1b/mnt.0",
            "pid": "29377",
            "root": "/"
        }
    }
]
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  2. Evict the specified CephFS client:

    Syntax

    ceph tell DAEMON_NAME client evict id=ID_NUMBER
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    Example

    [ceph: root@host01 /]# ceph tell mds.0 client evict id=4305
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In some situations, it can be useful to allow a previously blocklisted Ceph File System (CephFS) client to reconnect to the storage cluster.

Important

Removing a CephFS client from the blocklist puts data integrity at risk, and does not guarantee a fully healthy, and functional CephFS client as a result. The best way to get a fully healthy CephFS client back after an eviction, is to unmount the CephFS client and do a fresh mount. If other CephFS clients are accessing files that the blocklisted CephFS client was buffering I/O to, it can result in data corruption.

Prerequisites

  • Root-level access to the Ceph Monitor node.

Procedure

  1. Review the blocklist:

    Example

    [ceph: root@host01 /]# ceph osd blocklist ls

listed 1 entries
127.0.0.1:0/3710147553 2022-05-09 11:32:24.716146
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  2. Remove the CephFS client from the blocklist:

    Syntax

    ceph osd blocklist rm CLIENT_NAME_OR_IP_ADDR
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    Example

    [ceph: root@host01 /]# ceph osd blocklist rm 127.0.0.1:0/3710147553

un-blocklisting 127.0.0.1:0/3710147553
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  3. Optionally, you can have kernel-based CephFS clients automatically reconnect when removing them from the blocklist. On the kernel-based CephFS client, set the following option to clean either when doing a manual mount, or automatically mounting with an entry in the /etc/fstab file: 

    recover_session=clean
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  4. Optionally, you can have FUSE-based CephFS clients automatically reconnect when removing them from the blocklist. On the FUSE client, set the following option to true either when doing a manual mount, or automatically mounting with an entry in the /etc/fstab file: 

    client_reconnect_stale=true
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Chapter 6. Ceph File System quotas
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As a storage administrator, you can view, set, and remove quotas on any directory in the file system. You can place quota restrictions on the number of bytes or the number of files within the directory.

Prerequisites

  • A running, and healthy Red Hat Ceph Storage cluster.
  • Deployment of a Ceph File System.
  • Make sure that the attr package is installed.

6.1. Ceph File System quotas
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The Ceph File System (CephFS) quotas allow you to restrict the number of bytes or the number of files stored in the directory structure. Ceph File System quotas are fully supported using a FUSE client or using Kernel clients, version 4.17 or newer.

Limitations

  • CephFS quotas rely on the cooperation of the client mounting the file system to stop writing data when it reaches the configured limit. However, quotas alone cannot prevent an adversarial, untrusted client from filling the file system.
  • Once processes that write data to the file system reach the configured limit, a short period of time elapses between when the amount of data reaches the quota limit, and when the processes stop writing data. The time period generally measures in the tenths of seconds. However, processes continue to write data during that time. The amount of additional data that the processes write depends on the amount of time elapsed before they stop.
  • When using path-based access restrictions, be sure to configure the quota on the directory to which the client is restricted, or to a directory nested beneath it. If the client has restricted access to a specific path based on the MDS capability, and the quota is configured on an ancestor directory that the client cannot access, the client will not enforce the quota. For example, if the client cannot access the /home/ directory and the quota is configured on /home/, the client cannot enforce that quota on the directory /home/user/.
  • Snapshot file data that has been deleted or changed does not count towards the quota.
  • No support for quotas with NFS clients when using setxattr, and no support for file-level quotas on NFS. To use quotas on NFS shares, you can export them using subvolumes and setting the --size option.

6.2. Viewing quotas
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Use the getfattr command and the ceph.quota extended attributes to view the quota settings for a directory.

Note

If the attributes appear on a directory inode, then that directory has a configured quota. If the attributes do not appear on the inode, then the directory does not have a quota set, although its parent directory might have a quota configured. If the value of the extended attribute is 0, the quota is not set.

Prerequisites

  • Root-level access to the Ceph client node.
  • The attr package is installed.

Procedure

  1. To view CephFS quotas.

    1. Using a byte-limit quota:

      Syntax

      getfattr -n ceph.quota.max_bytes DIRECTORY
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      Example

      [root@client ~]# getfattr -n ceph.quota.max_bytes /mnt/cephfs/
getfattr: Removing leading '/' from absolute path names
# file: mnt/cephfs/
ceph.quota.max_bytes="100000000"
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      In this example, 100000000 equals 100 MB.

    2. Using a file-limit quota:

      Syntax

      getfattr -n ceph.quota.max_files DIRECTORY
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      Example

      [root@client ~]# getfattr -n ceph.quota.max_files /mnt/cephfs/
getfattr: Removing leading '/' from absolute path names
# file: mnt/cephfs/
ceph.quota.max_files="10000"
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      In this example, 10000 equals 10,000 files.

6.3. Setting quotas
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This section describes how to use the setfattr command and the ceph.quota extended attributes to set the quota for a directory.

Prerequisites

  • Root-level access to the Ceph client node.
  • The attr package is installed.

Procedure

  • Set the quota for a direcotry by using a byte-limit quota:

    Note

    The following values are supported for byte-limit quota: K, Ki, M, Mi, G, Gi, T, and Ti.

    Syntax

    setfattr -n ceph.quota.max_bytes -v LIMIT_VALUE DIRECTORY
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    Example

    [root@client ~]# setfattr -n ceph.quota.max_bytes -v 2T /cephfs/
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  • Set the quota for a directory by using a file-limit quota:

    Syntax

    setfattr -n ceph.quota.max_files -v LIMIT_VALUE DIRECTORY
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    Example

    [root@client ~]# setfattr -n ceph.quota.max_files -v 10000 /cephfs/
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    In this example, 10000 equals 10,000 files.

    Note

    Only numerical values are supported for the file LIMIT_VALUE.

6.4. Removing quotas
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This section describes how to use the setfattr command and the ceph.quota extended attributes to remove a quota from a directory.

Prerequisites

  • Root-level access to the Ceph client node.
  • Make sure that the attr package is installed.

Procedure

  1. To remove CephFS quotas.

    1. Using a byte-limit quota:

      Syntax

      setfattr -n ceph.quota.max_bytes -v 0 DIRECTORY
      Copy to Clipboard Toggle word wrap

      Example

      [root@client ~]# setfattr -n ceph.quota.max_bytes -v 0 /mnt/cephfs/
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    2. Using a file-limit quota:

      Syntax

      setfattr -n ceph.quota.max_files -v 0 DIRECTORY
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      Example

      [root@client ~]# setfattr -n ceph.quota.max_files -v 0 /mnt/cephfs/
      Copy to Clipboard Toggle word wrap

Chapter 7. File and directory layouts
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As a storage administrator, you can control how file or directory data is mapped to objects.

This section describes how to:

Prerequisites

  • A running, and healthy Red Hat Ceph Storage cluster.
  • Deployment of a Ceph File System.
  • The installation of the attr package.

7.1. Overview of file and directory layouts
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This section explains what file and directory layouts are in the context for the Ceph File System.

A layout of a file or directory controls how its content is mapped to Ceph RADOS objects. The directory layouts serve primarily for setting an inherited layout for new files in that directory.

To view and set a file or directory layout, use virtual extended attributes or extended file attributes (xattrs). The name of the layout attributes depends on whether a file is a regular file or a directory:

  • Regular files layout attributes are called ceph.file.layout.
  • Directories layout attributes are called ceph.dir.layout.

Layouts Inheritance

Files inherit the layout of their parent directory when you create them. However, subsequent changes to the parent directory layout do not affect children. If a directory does not have any layouts set, files inherit the layout from the closest directory to the layout in the directory structure.

7.2. Setting file and directory layout fields
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Use the setfattr command to set layout fields on a file or directory.

Important

When you modify the layout fields of a file, the file must be empty, otherwise an error occurs.

Prerequisites

  • Root-level access to the node.

Procedure

  • To modify layout fields on a file or directory:

    Syntax

    setfattr -n ceph.TYPE.layout.FIELD -v VALUE PATH
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    Replace:

    • TYPE with file or dir.
    • FIELD with the name of the field.
    • VALUE with the new value of the field.
    • PATH with the path to the file or directory.

    Example

    [root@mon ~]# setfattr -n ceph.file.layout.stripe_unit -v 1048576 test
    Copy to Clipboard Toggle word wrap

Additional Resources

7.3. Viewing file and directory layout fields
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To use the getfattr command to view layout fields on a file or directory.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to all nodes in the storage cluster.

Procedure

  • To view layout fields on a file or directory as a single string:

    Syntax

    getfattr -n ceph.TYPE.layout PATH
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    Replace
    • PATH with the path to the file or directory.
    • TYPE with file or dir.

    Example

    [root@mon ~]# getfattr -n ceph.dir.layout /home/test
ceph.dir.layout="stripe_unit=4194304 stripe_count=2 object_size=4194304 pool=cephfs_data"
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Note

A directory does not have an explicit layout until you set it. Consequently, attempting to view the layout without first setting it fails because there are no changes to display.

Additional Resources

7.4. Viewing individual layout fields
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Use the getfattr command to view individual layout fields for a file or directory.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to all nodes in the storage cluster.

Procedure

  • To view individual layout fields on a file or directory:

    Syntax

    getfattr -n ceph.TYPE.layout.FIELD _PATH
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    Replace
    • TYPE with file or dir.
    • FIELD with the name of the field.
    • PATH with the path to the file or directory.

    Example

    [root@mon ~]# getfattr -n ceph.file.layout.pool test
ceph.file.layout.pool="cephfs_data"
    Copy to Clipboard Toggle word wrap

    Note

    Pools in the pool field are indicated by name. However, newly created pools can be indicated by ID.

Additional Resources

  • The getfattr(1) manual page.

7.5. Removing directory layouts
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Use the setfattr command to remove layouts from a directory.

Note

When you set a file layout, you cannot change or remove it.

Prerequisites

  • A directory with a layout.

Procedure

  1. To remove a layout from a directory:

    Syntax

    setfattr -x ceph.dir.layout DIRECTORY_PATH
    Copy to Clipboard Toggle word wrap

    Example

    [user@client ~]$ setfattr -x ceph.dir.layout /home/cephfs
    Copy to Clipboard Toggle word wrap

  2. To remove the pool_namespace field:

    Syntax

    setfattr -x ceph.dir.layout.pool_namespace DIRECTORY_PATH
    Copy to Clipboard Toggle word wrap

    Example

    [user@client ~]$ setfattr -x ceph.dir.layout.pool_namespace /home/cephfs
    Copy to Clipboard Toggle word wrap

    Note

    The pool_namespace field is the only field you can remove separately.

Additional Resources

  • The setfattr(1) manual page

Chapter 8. Ceph File System snapshots
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As a storage administrator, you can take a point-in-time snapshot of a Ceph File System (CephFS) directory. CephFS snapshots are asynchronous, and you can choose which directory snapshots are created in.

Prerequisites

  • A running, and healthy Red Hat Ceph Storage cluster.
  • Deployment of a Ceph File System.

8.1. Ceph File System snapshots
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The Ceph File System (CephFS) snapshotting feature is enabled by default on new Ceph File Systems, but must be manually enabled on existing Ceph File Systems. CephFS snapshots create an immutable, point-in-time view of a Ceph File System. CephFS snapshots are asynchronous and are kept in a special hidden directory in the CephFS directory named .snap. You can specify snapshot creation for any directory within a Ceph File System. When specifying a directory, the snapshot also includes all the subdirectories beneath it.

Warning

Each Ceph Metadata Server (MDS) cluster allocates the snap identifiers independently. Using snapshots for multiple Ceph File Systems that are sharing a single pool causes snapshot collisions, and results in missing file data.

8.2. Creating a snapshot for a Ceph File System
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You can create an immutable, point-in-time view of a Ceph File System (CephFS) by creating a snapshot.

Note

For a new Ceph File System, snapshots are enabled by default.

Prerequisites

  • A running, and healthy Red Hat Ceph Storage cluster.
  • Deployment of a Ceph File System.
  • Root-level access to a Ceph Metadata Server (MDS) node.

Procedure

  1. Log into the Cephadm shell:

    Example

    [root@mds ~]# cephadm shell
    Copy to Clipboard Toggle word wrap

  2. For existing Ceph File Systems, enable the snapshotting feature:

    Syntax

    ceph fs set FILE_SYSTEM_NAME allow_new_snaps true
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@mds ~]# ceph fs set cephfs01 allow_new_snaps true
    Copy to Clipboard Toggle word wrap

  3. Create a new snapshot subdirectory under the .snap directory:

    Syntax

    mkdir NEW_DIRECTORY_PATH
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@mds ~]# mkdir /.snap/new-snaps
    Copy to Clipboard Toggle word wrap

    This example creates the new-snaps subdirectory, and this informs the Ceph Metadata Server (MDS) to start making snapshots.

    1. To delete snapshots:

      Syntax

      rmdir NEW_DIRECTORY_PATH
      Copy to Clipboard Toggle word wrap

      Example

      [ceph: root@mds ~]# rmdir /.snap/new-snaps
      Copy to Clipboard Toggle word wrap

      Important

      Attempting to delete root-level snapshots, which might contain underlying snapshots, will fail.

Chapter 9. Ceph File System snapshot scheduling
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As a storage administrator, you can take a point-in-time snapshot of a Ceph File System (CephFS) directory. CephFS snapshots are asynchronous, and you can choose which directory snapshots are created in.

Prerequisites

  • A running, and healthy Red Hat Ceph Storage cluster.
  • Deployment of a Ceph File System.

9.1. Ceph File System snapshot schedules
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A Ceph File System (CephFS) can schedule snapshots of a file system directory. The scheduling of snapshots is managed by the Ceph Manager, and relies on Python Timers. The snapshot schedule data is stored as an object in the CephFS metadata pool, and at runtime, all the schedule data lives in a serialized SQLite database.

Important

The scheduler is precisely based on the specified time to keep snapshots apart when a storage cluster is under normal load. When the Ceph Manager is under a heavy load, it’s possible that a snapshot might not get scheduled right away, resulting in a slightly delayed snapshot. If this happens, then the next scheduled snapshot acts as if there was no delay. Scheduled snapshots that are delayed do not cause drift in the overall schedule.

Usage

Scheduling snapshots for a Ceph File System (CephFS) is managed by the snap_schedule Ceph Manager module. This module provides an interface to add, query, and delete snapshot schedules, and to manage the retention policies. This module also implements the ceph fs snap-schedule command, with several subcommands to manage schedules, and retention policies. All of the subcommands take the CephFS volume path and subvolume path arguments to specify the file system path when using multiple Ceph File Systems. Not specifying the CephFS volume path, the argument defaults to the first file system listed in the fs_map, and not specifying the subvolume path argument defaults to nothing.

Snapshot schedules are identified by the file system path, the repeat interval, and the start time. The repeat interval defines the time between two subsequent snapshots. The interval format is a number plus a time designator: h(our), d(ay), or w(eek). For example, having an interval of 4h, means one snapshot every four hours. The start time is a string value in the ISO format, %Y-%m-%dT%H:%M:%S, and if not specified, the start time uses a default value of last midnight. For example, you schedule a snapshot at 14:45, using the default start time value, with a repeat interval of 1h, the first snapshot will be taken at 15:00.

Retention policies are identified by the file system path, and the retention policy specifications. Defining a retention policy consist of either a number plus a time designator or a concatenated pairs in the format of COUNT TIME_PERIOD. The policy ensures a number of snapshots are kept, and the snapshots are at least for a specified time period apart. The time period designators are: h(our), d(ay), w(eek), M(onth), Y(ear), and n. The n time period designator is a special modifier, which means keep the last number of snapshots regardless of timing. For example, 4d means keeping four snapshots that are at least one day, or longer apart from each other.

Add a snapshot schedule for a CephFS path that does not exist yet. You can create one or more schedules for a single path. Schedules are considered different, if their repeat interval and start times are different.

A CephFS path can only have one retention policy, but a retention policy can have multiple count-time period pairs.

Note

Once the scheduler module is enabled, running the ceph fs snap-schedule command displays the available subcommands and their usage format.

Prerequisites

  • A running, and healthy Red Hat Ceph Storage cluster.
  • Deployment of a Ceph File System.
  • Root-level access to a Ceph Manager and Metadata Server (MDS) nodes.
  • Enable CephFS snapshots on the file system.

Procedure

  1. Log into the Cephadm shell on a Ceph Manager node:

    Example

    [root@host01 ~]# cephadm shell
    Copy to Clipboard Toggle word wrap

  2. Enable the snap_schedule module:

    Example

    [ceph: root@host01 /]# ceph mgr module enable snap_schedule
    Copy to Clipboard Toggle word wrap

  3. Log into the client node:

    Example

    [root@host02 ~]# cephadm shell
    Copy to Clipboard Toggle word wrap

  4. Add a new schedule for a Ceph File System:

    Syntax

    ceph fs snap-schedule add FILE_SYSTEM_VOLUME_PATH REPEAT_INTERVAL [START_TIME] --fs CEPH_FILE_SYSTEM_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 /]# ceph fs snap-schedule add /cephfs_kernelf739cwtus2/pmo9axbwsi 1h 2022-06-27T21:50:00 --fs mycephfs
    Copy to Clipboard Toggle word wrap

    Note

    START_TIME is represented in ISO 8601 format.

    This example creates a snapshot schedule for the path /cephfs within the filesystem mycephfs, snapshotting every hour, and starts on 27 June 2022 9:50 PM.

  5. Add a new retention policy for snapshots of a CephFS volume path:

    Syntax

    ceph fs snap-schedule retention add FILE_SYSTEM_VOLUME_PATH [COUNT_TIME_PERIOD_PAIR] TIME_PERIOD COUNT
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 /]# ceph fs snap-schedule retention add /cephfs h 14
    1 
    
[ceph: root@host02 /]# ceph fs snap-schedule retention add /cephfs d 4
    2 
    
[ceph: root@host02 /]# ceph fs snap-schedule retention add /cephfs 14h4w
    3
    Copy to Clipboard Toggle word wrap

    1
    This example keeps 14 snapshots at least one hour apart.
    2
    This example keeps 4 snapshots at least one day apart.
    3
    This example keeps 14 hourly, and 4 weekly snapshots.

  6. List the snapshot schedules to verify the new schedule is created.

    Syntax

    ceph fs snap-schedule list FILE_SYSTEM_VOLUME_PATH [--format=plain|json] [--recursive=true]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 /]# ceph fs snap-schedule list /cephfs --recursive=true
    Copy to Clipboard Toggle word wrap

    This example lists all schedules in the directory tree.

  7. Check the status of a snapshot schedule:

    Syntax

    ceph fs snap-schedule status FILE_SYSTEM_VOLUME_PATH [--format=plain|json]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 /]# ceph fs snap-schedule status /cephfs --format=json
    Copy to Clipboard Toggle word wrap

    This example displays the status of the snapshot schedule for the CephFS /cephfs path in JSON format. The default format is plain text, if not specified.

To manage the retention policies for Ceph File System (CephFS) subvolume snapshots, you can have different schedules for a single path.

Schedules are considered different, if their repeat interval and start times are different.

Add a snapshot schedule for a CephFS file path that does not exist yet. A CephFS path can only have one retention policy, but a retention policy can have multiple count-time period pairs.

Note

Once the scheduler module is enabled, running the ceph fs snap-schedule command displays the available subcommands and their usage format.

Prerequisites

  • A working Red Hat Ceph Storage cluster with Ceph File System (CephFS) deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS subvolume and subvolume group created.

You can create a snapshot schedule for:

  • A directory in a subvolume.
  • A subvolume in default group.
  • A subvolume in non-default group.

However, the commands are different.

Procedure

  • To create a snapshot schedule for a directory in the subvolume:

    1. Get the absolute path of the subvolume where directory exists:

      Syntax

      ceph fs subvolume getpath VOLUME_NAME SUBVOLUME_NAME SUBVOLUME_GROUP_NAME
      Copy to Clipboard Toggle word wrap

      Example

      [ceph: root@host02 /]# ceph fs subvolume getpath cephfs subvol_1 subvolgroup_1
      Copy to Clipboard Toggle word wrap

    2. Add a snapshot schedule to a directory in the subvolume:

      Syntax

      ceph fs snap-schedule add SUBVOLUME_DIR_PATH SNAP_SCHEDULE [START_TIME] --fs CEPH_FILE_SYSTEM_NAME --subvol SUBVOLUME_NAME
      Copy to Clipboard Toggle word wrap

      Note

      Path in snap-schedule command would be <absolute_path_of_ subvolume>/<relative_path_of_test_dir>, refer step1 for absolute_path of subvolume.

      Example

      [ceph: root@host02 /]# ceph fs snap-schedule add /cephfs_kernelf739cwtus2/pmo9axbwsi 1h 2022-06-27T21:50:00 --fs cephfs --subvol subvol_1
Schedule set for path /..
      Copy to Clipboard Toggle word wrap

      Note

      START_TIME is represented in ISO 8601 format.

      This example creates a snapshot schedule for the subvolume path, snapshotting every hour, and starts on 27 June 2022 9:50 PM.

  • To create a snapshot schedule for a subvolume in a default group, run the following command:

    Syntax

    ceph fs snap-schedule add /.. SNAP_SCHEDULE [START_TIME] --fs CEPH_FILE_SYSTEM_NAME --subvol _SUBVOLUME_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 /]# ceph fs snap-schedule add - 2M --subvol sv_non_def_1
    Copy to Clipboard Toggle word wrap

    Note

    The path must be defined and cannot be left empty.There is no dependency on path string value, you can define it as /, -` or /...

  • To create a snapshot schedule for a subvolume in a non-default group, run the following command:

    Syntax

    ceph fs snap-schedule add /.. SNAP_SCHEDULE [START_TIME] --fs CEPH_FILE_SYSTEM_NAME --subvol _SUBVOLUME_NAME --group NON_DEFAULT_SUBVOLGROUP_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 /]# ceph fs snap-schedule add - 2M --fs cephfs --subvol sv_non_def_1 --group svg1
    Copy to Clipboard Toggle word wrap

    Note

    The path must be defined and cannot be left empty.There is no dependency on path string value, you can define it as /, -` or /...

To define how many snapshots to retain in the volume path at any time, you must add a retention policy after you have created a snapshot schedule.

You can create retention policies for directories within a subvolume group, subvolume within the default group and to the subvolume withing a non-default group.

Prerequisites

  • A running and healthy IBM Storage Ceph cluster with Ceph File System (CephFS) deployed.
  • A minimum of read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS subvolume and subvolume group created.
  • A snapshot schedule.

Procedure

  • Add a new retention policy for snapshot schedules in a directory of a CephFS subvolume:

    Syntax

    ceph fs snap-schedule retention add SUBVOLUME_DIR_PATH [COUNT_TIME_PERIOD_PAIR] TIME_PERIOD COUNT
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 /]# ceph fs snap-schedule retention add /volumes/_nogroup/subvol_1/85a615da-e8fa-46c1-afc3-0eb8ae64a954/.. h 14
    1 
    
[ceph: root@host02 /]# ceph fs snap-schedule retention add /volumes/_nogroup/subvol_1/85a615da-e8fa-46c1-afc3-0eb8ae64a954/.. d 4
    2 
    
[ceph: root@host02 /]# ceph fs snap-schedule retention add /volumes/_nogroup/subvol_1/85a615da-e8fa-46c1-afc3-0eb8ae64a954/.. 14h4w
    3 
    

Retention added to path /volumes/_nogroup/subvol_1/85a615da-e8fa-46c1-afc3-0eb8ae64a954/..
    Copy to Clipboard Toggle word wrap

    1
    This example keeps 14 snapshots at least one hour apart.
    2
    This example keeps 4 snapshots at least one day apart.
    3
    This example keeps 14 hourly, and 4 weekly snapshots.

  • Add a retention policy to a snapshot schedule created for a subvolume in the default group:

    Syntax

    ceph fs snap-schedule retention add / [COUNT_TIME_PERIOD_PAIR] TIME_PERIOD_COUNT --fs CEPH_FILE_SYSTEM_NAME --subvol SUBVOLUME_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 /]# ceph fs snap-schedule retention add / 5h --fs cephfs --subvol sv_sched
Retention added to path /volumes/sv_sched/e704342a-ff07-4763-bb0b-a46d9dda6f27/..
    Copy to Clipboard Toggle word wrap

    Important

    The path ( / ) must be defined and cannot be left empty. There is no dependency on path string value, you can define it as /, - or /…​

  • Add a retention policy to the snapshot schedule created for a subvolume group in the non-default group:

    Syntax

    ceph fs snap-schedule retention add / [COUNT_TIME_PERIOD_PAIR] TIME_PERIOD_COUNT --fs CEPH_FILE_SYSTEM_NAME --subvol SUBVOLUME_NAME --group NON_DEFAULT_SUBVOLGROUP_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 /]# ceph fs snap-schedule retention add / 5h --fs cephfs --subvol sv_sched --group subvolgroup_cg
Retention added to path /volumes/subvolgroup_cg/sv_sched/e704342a-ff07-4763-bb0b-a54j0dda7f16/..
    Copy to Clipboard Toggle word wrap

    Important

    The path ( / ) must be defined and cannot be left empty. There is no dependency on path string value, you can define it as /, - or /…​

9.3.2. Listing CephFS snapshot schedules
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By listing and adhering to snapshot schedules, you can ensure robust data protection and efficient management.

Prerequisites

  • A running and healthy IBM Storage Ceph cluster with Ceph File System (CephFS) deployed.
  • A minimum of read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS subvolume and subvolume group created.
  • A snapshot schedule.

Procedure

  • List the snapshot schedules:

    Syntax

    ceph fs snap-schedule list SUBVOLUME_VOLUME_PATH [--format=plain|json] [--recursive=true]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 /]# ceph fs snap-schedule list / --recursive=true

/volumes/_nogroup/subv1/85a615da-e8fa-46c1-afc3-0eb8ae64a954/.. 4h
    Copy to Clipboard Toggle word wrap

    This example lists all schedules in the directory tree.

You can check the status of snapshot schedules using the command in the procedure for snapshots created in a directory of a subvolume, for a subvolume in the default subvolume group and for a subvolume created in a non-default group.

Prerequisites

  • A running and healthy IBM Storage Ceph cluster with Ceph File System (CephFS) deployed.
  • A minimum of read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • A CephFS subvolume and subvolume group created.
  • A snapshot schedule.

Procedure

  • Check the status of a snapshot schedule created for a directory in the subvolume:

    Syntax

    ceph fs snap-schedule status SUBVOLUME_DIR_PATH [--format=plain|json]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 /]# ceph fs snap-schedule status /volumes/_nogroup/subv1/85a615da-e8fa-46c1-afc3-0eb8ae64a954/.. --format=json

{"fs": "cephfs", "subvol": "subvol_1", "path": "/volumes/_nogroup/subvol_1/85a615da-e8fa-46c1-afc3-0eb8ae64a954/..", "rel_path": "/..", "schedule": "4h", "retention": {"h": 14}, "start": "2022-05-16T14:00:00", "created": "2023-03-20T08:47:18", "first": null, "last": null, "last_pruned": null, "created_count": 0, "pruned_count": 0, "active": true}
    Copy to Clipboard Toggle word wrap

    This example displays the status of the snapshot schedule for the /volumes/_nogroup/subv1/85a615da-e8fa-46c1-afc3-0eb8ae64a954/.. path in JSON format. The default format is plain text, if not specified.

  • Check the status of the snapshot schedule created for a subvolume in the default group:

    Syntax

    ceph fs snap-schedule status --fs CEPH_FILE_SYSTEM_NAME --subvol SUBVOLUME_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 /]# ceph fs snap-schedule status --fs cephfs --subvol sv_sched
{"fs": "cephfs", "subvol": "sv_sched", "group": "subvolgroup_cg", "path": "/volumes/subvolgroup_cg/sv_sched/e704342a-ff07-4763-bb0b-a46d9dda6f27/..", "rel_path": "/volumes/subvolgroup_cg/sv_sched/e704342a-ff07-4763-bb0b-a46d9dda6f27/..", "schedule": "1h", "retention": {"h": 5}, "start": "2024-05-21T00:00:00", "created": "2024-05-21T09:18:58", "first": null, "last": null, "last_pruned": null, "created_count": 0, "pruned_count": 0, "active": true}
    Copy to Clipboard Toggle word wrap

    Important

    The path ( / ) must be defined and cannot be left empty. There is no dependency on path string value, you can define it as /, - or /…​

  • Check the status of the snapshot schedule created for a subvolume in the non-default group: .Syntax 
ceph fs snap-schedule status --fs _CEPH_FILE_SYSTEM_NAME_ --subvol _SUBVOLUME_NAME_ --group _NON-DEFAULT_SUBVOLGROUP_NAME_
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Example

[ceph: root@host02 /]# ceph fs snap-schedule status --fs cephfs --subvol sv_sched --group subvolgroup_cg
{"fs": "cephfs", "subvol": "sv_sched", "group": "subvolgroup_cg", "path": "/volumes/subvolgroup_cg/sv_sched/e564329a-kj87-4763-gh0y-b56c8sev7t23/..", "rel_path": "/volumes/subvolgroup_cg/sv_sched/e704342a-ff07-4763-bb0b-a46d9dda6f27/..", "schedule": "1h", "retention": {"h": 5}, "start": "2024-05-21T00:00:00", "created": "2024-05-21T09:18:58", "first": null, "last": null, "last_pruned": null, "created_count": 0, "pruned_count": 0, "active": true}
Copy to Clipboard Toggle word wrap

+ IMPORTANT: The path ( / ) must be defined and cannot be left empty. There is no dependency on path string value, you can define it as /, - or /…​

This section provides the steps to manually set the snapshot schedule to active for a Ceph File System (CephFS).

Prerequisites

  • A working Red Hat Ceph Storage cluster with a Ceph File System (CephFS) deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.

Procedure

  • Activate the snapshot schedule:

    Syntax

    ceph fs snap-schedule activate FILE_SYSTEM_VOLUME_PATH [REPEAT_INTERVAL]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs snap-schedule activate /cephfs
    Copy to Clipboard Toggle word wrap

    This example activates all schedules for the CephFS /cephfs path.

This section provides the steps to manually set the snapshot schedule to active for a Ceph File System (CephFS) sub volume.

Prerequisites

  • A working Red Hat Ceph Storage cluster with a Ceph File System (CephFS) deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.

Procedure

  • Activate the snapshot schedule created for a directory in a subvolume:

    Syntax

    ceph fs snap-schedule activate SUBVOL_DIR_PATH [REPEAT_INTERVAL]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs snap-schedule activate /volumes/_nogroup/subvol_1/85a615da-e8fa-46c1-afc3-0eb8ae64a954/..
    Copy to Clipboard Toggle word wrap

    This example activates all schedules for the CephFS /volumes/_nogroup/subvol_1/85a615da-e8fa-46c1-afc3-0eb8ae64a954/.. path.

  • Activate the snapshot schedule created for a subvolume in the default group:

    Syntax

    ceph fs snap-schedule activate /.. REPEAT_INTERVAL --fs CEPH_FILE_SYSTEM_NAME --subvol SUBVOLUME_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 /]# ceph fs snap-schedule activate / --fs cephfs --subvol sv_sched
Schedule activated for path /volumes/subvolgroup_cg/sv_sched/e704342a-ff07-4763-bb0b-a46d9dda6f27/..
    Copy to Clipboard Toggle word wrap

    Important

    The path ( / ) must be defined and cannot be left empty. There is no dependency on path string value, you can define it as /, - or /…​

  • Activate the snapshot schedule created for a subvolume in the non-default group:

    Syntax

    ceph fs snap-schedule activate /.. [REPEAT_INTERVAL] --fs CEPH_FILE_SYSTEM_NAME --subvol SUBVOLUME_NAME --group NON-DEFAULT_GROUP_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 /]# ceph fs snap-schedule activate / --fs cephfs --subvol sv_sched --group subvolgroup_cg
Schedule activated for path /volumes/subvolgroup_cg/sv_sched/e704342a-ff07-4763-bb0b-a46d9dda6f27/..
    Copy to Clipboard Toggle word wrap

    Important

    The path ( / ) must be defined and cannot be left empty. There is no dependency on path string value, you can define it as /, - or /…​

This section provides the steps to manually set the snapshot schedule to inactive for a Ceph File System (CephFS). This action will exclude the snapshot from scheduling until it is activated again.

Prerequisites

  • A working Red Hat Ceph Storage cluster with a Ceph File System (CephFS) deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • Snapshot schedule is created and is in active state.

Procedure

  • Deactivate a snapshot schedule for a CephFS path:

    Syntax

    ceph fs snap-schedule deactivate FILE_SYSTEM_VOLUME_PATH [REPEAT_INTERVAL]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 ~]# ceph fs snap-schedule deactivate /cephfs 1d
    Copy to Clipboard Toggle word wrap

    This example deactivates the daily snapshots for the /cephfs path, thereby pausing any further snapshot creation.

This section provides the steps to manually set the snapshot schedule to inactive for a Ceph File System (CephFS) sub volume. This action excludes the snapshot from scheduling until it is activated again.

Prerequisites

  • A working Red Hat Ceph Storage cluster with a Ceph File System (CephFS) deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • Snapshot schedule is created and is in active state.

Procedure

  • Deactivate a snapshot schedule for a directory in a CephFS subvolume:

    Syntax

    ceph fs snap-schedule deactivate SUBVOL_DIR_PATH [REPEAT_INTERVAL]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 ~]# ceph fs snap-schedule deactivate /volumes/_nogroup/subvol_1/85a615da-e8fa-46c1-afc3-0eb8ae64a954/.. 1d
    Copy to Clipboard Toggle word wrap

    This example deactivates the daily snapshots for the /volumes/_nogroup/subvol_1/85a615da-e8fa-46c1-afc3-0eb8ae64a954/.. path, thereby pausing any further snapshot creation.

  • Deactivate the snapshot schedule created for a subvolume in the default group:

    Syntax

    ceph fs snap-schedule deactivate / REPEAT_INTERVAL --fs CEPH_FILE_SYSTEM_NAME --subvol SUBVOLUME_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 ~]# ceph fs snap-schedule deactivate / --fs cephfs --subvol sv_sched
Schedule deactivated for path /volumes/subvolgroup_cg/sv_sched/e704342a-ff07-4763-bb0b-a46d9dda6f27/..
    Copy to Clipboard Toggle word wrap

    Important

    The path ( / ) must be defined and cannot be left empty. There is no dependency on path string value, you can define it as /, - or /…​

  • Deactivate the snapshot schedule created for a subvolume in the non-default group:

    Syntax

    ceph fs snap-schedule deactivate / REPEAT_INTERVAL --fs CEPH_FILE_SYSTEM_NAME --subvol SUBVOLUME_NAME --group NON-DEFAULT_GROUP_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 ~]# ceph fs snap-schedule deactivate / --fs cephfs --subvol sv_sched --group subvolgroup_cg
Schedule deactivated for path /volumes/subvolgroup_cg/sv_sched/e704342a-ff07-4763-bb0b-a46d9dda6f27/..
    Copy to Clipboard Toggle word wrap

    Important

    The path ( / ) must be defined and cannot be left empty. There is no dependency on path string value, you can define it as /, - or /…​

This section provides the step to remove snapshot schedule of a Ceph File System (CephFS).

Prerequisites

  • A working Red Hat Ceph Storage cluster with a Ceph File System (CephFS) deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • Snapshot schedule is created.

Procedure

  1. Remove a specific snapshot schedule:

    Syntax

    ceph fs snap-schedule remove FILE_SYSTEM_VOLUME_PATH [REPEAT_INTERVAL] [START_TIME]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 ~]# ceph fs snap-schedule remove /cephfs 4h 2022-05-16T14:00:00
    Copy to Clipboard Toggle word wrap

    This example removes the specific snapshot schedule for the /cephfs volume, that is snapshotting every four hours, and started on 16 May 2022 2:00 PM.

  2. Remove all snapshot schedules for a specific CephFS volume path:

    Syntax

    ceph fs snap-schedule remove FILE_SYSTEM_VOLUME_PATH
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 ~]# ceph fs snap-schedule remove /cephfs
    Copy to Clipboard Toggle word wrap

    This example removes all the snapshot schedules for the /cephfs volume path.

This section provides the step to remove snapshot schedule of a Ceph File System (CephFS) sub volume.

Prerequisites

  • A working Red Hat Ceph Storage cluster with a Ceph File System (CephFS) deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • Snapshot schedule is created.

Procedure

  • Remove a specific snapshot schedule created for a directory in a CephFS subvolume:

    Syntax

    ceph fs snap-schedule remove SUBVOL_DIR_PATH [REPEAT_INTERVAL] [START_TIME]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 ~]# ceph fs snap-schedule remove /volumes/_nogroup/subvol_1/85a615da-e8fa-46c1-afc3-0eb8ae64a954/.. 4h 2022-05-16T14:00:00
    Copy to Clipboard Toggle word wrap

    This example removes the specific snapshot schedule for the /volumes/_nogroup/subvol_1/85a615da-e8fa-46c1-afc3-0eb8ae64a954/.. volume, that is snapshotting every four hours, and started on 16 May 2022 2:00 PM.

  • Remove a specific snapshot schedule created for a subvolume in the default group:

    Syntax

    ceph fs snap-schedule remove / --fs CEPH_FILESYSTEM_NAME --subvol SUBVOLUME_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 ~]# ceph fs snap-schedule remove / --fs cephfs --subvol sv_sched
Schedule removed for path /volumes/subvolgroup_cg/sv_sched/e704342a-ff07-4763-bb0b-a46d9dda6f27/..
    Copy to Clipboard Toggle word wrap

    Important

    The path ( / ) must be defined and cannot be left empty. There is no dependency on path string value, you can define it as /, - or /…​

  • Remove a specific snapshot schedule created for a subvolume in the non-default group:

    Syntax

    ceph fs snap-schedule remove / --fs CEPH_FILESYSTEM_NAME --subvol SUBVOLUME_NAME --group NON-DEFAULT_GROUP_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 ~]# ceph fs snap-schedule remove / --fs cephfs --subvol sv_sched --group subvolgroup_cg
Schedule removed for path /volumes/subvolgroup_cg/sv_sched/e704342a-ff07-4763-bb0b-a46d9dda6f27/..
    Copy to Clipboard Toggle word wrap

    Important

    The path ( / ) must be defined and cannot be left empty. There is no dependency on path string value, you can define it as /, - or /…​

This section provides the step to remove the retention policy of the scheduled snapshots for a Ceph File System (CephFS).

Prerequisites

  • A working Red Hat Ceph Storage cluster with a Ceph File System (CephFS) deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • Snapshot schedule created for a CephFS volume path.

Procedure

  • Remove a retention policy on a CephFS path:

    Syntax

    ceph fs snap-schedule retention remove FILE_SYSTEM_VOLUME_PATH [COUNT_TIME_PERIOD_PAIR] TIME_PERIOD COUNT
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 ~]# ceph fs snap-schedule retention remove /cephfs h 4
    1 
    
[ceph: root@host02 ~]# ceph fs snap-schedule retention remove /cephfs 14d4w
    2
    Copy to Clipboard Toggle word wrap

    1
    This example removes 4 hourly snapshots.
    2
    This example removes 14 daily, and 4 weekly snapshots.

This section provides the step to remove the retention policy of the scheduled snapshots for a Ceph File System (CephFS) sub volume.

Prerequisites

  • A working Red Hat Ceph Storage cluster with a Ceph File System (CephFS) deployed.
  • At least read access on the Ceph Monitor.
  • Read and write capability on the Ceph Manager nodes.
  • Snapshot schedule created for a CephFS sub volume path.

Procedure

  • Remove a retention policy for a directory in a CephFS subvolume:

    Syntax

    ceph fs snap-schedule retention remove SUBVOL_DIR_PATH [COUNT_TIME_PERIOD_PAIR] TIME_PERIOD COUNT
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 ~]# ceph fs snap-schedule retention remove /volumes/_nogroup/subvol_1/85a615da-e8fa-46c1-afc3-0eb8ae64a954/.. h 4
    1 
    
[ceph: root@host02 ~]# ceph fs snap-schedule retention remove /volumes/_nogroup/subvol_1/85a615da-e8fa-46c1-afc3-0eb8ae64a954/.. 14d4w
    2
    Copy to Clipboard Toggle word wrap

    1
    This example removes 4 hourly snapshots.
    2
    This example removes 14 daily, and 4 weekly snapshots.

  • Remove a retention policy created on snapshot schedule for a subvolume in the default group:

    Syntax

    ceph fs snap-schedule retention remove / TIME_PERIOD_PAIR TIME_PERIOD COUNT --fs CEPH_FILESYSTEM_NAME --subvol SUBVOLUME_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 ~]# ceph fs snap-schedule retention remove / 5h --fs cephfs --subvol sv_sched --group subvolgroup_cg
Retention removed from path /volumes/subvolgroup_cg/sv_sched/e704342a-ff07-4763-bb0b-a46d9dda6f27/..
    Copy to Clipboard Toggle word wrap

    Important

    The path ( / ) must be defined and cannot be left empty. There is no dependency on path string value, you can define it as /, - or /…​

  • Remove a retention policy created on snapshot schedule for a subvolume in the non-default group:

    Syntax

    ceph fs snap-schedule retention remove / TIME_PERIOD_PAIR TIME_PERIOD COUNT --fs CEPH_FILESYSTEM_NAME --subvol SUBVOLUME_NAME --group NON-DEFAULT_GROUP_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host02 ~]# ceph fs snap-schedule retention remove / 5h --fs cephfs --subvol sv_sched --group subvolgroup_cg
Retention removed from path /volumes/subvolgroup_cg/sv_sched/e704342a-ff07-4763-bb0b-a46d9dda6f27/..
    Copy to Clipboard Toggle word wrap

    Important

    The path ( / ) must be defined and cannot be left empty. There is no dependency on path string value, you can define it as /, - or /…​

Chapter 10. Ceph File System snapshot mirroring
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As a storage administrator, you can replicate a Ceph File System (CephFS) to a remote Ceph File System on another Red Hat Ceph Storage cluster.

Prerequisites

  • The source and the target storage clusters must be running Red Hat Ceph Storage 6.0 or later.

The Ceph File System (CephFS) supports asynchronous replication of snapshots to a remote CephFS on another Red Hat Ceph Storage cluster. Snapshot synchronization copies snapshot data to a remote Ceph File System, and creates a new snapshot on the remote target with the same name. You can configure specific directories for snapshot synchronization.

Managing CephFS snapshot mirroring is done by the CephFS mirroring daemon (cephfs-mirror). This snapshot data is synchronized by doing a bulk copy to the remote CephFS. The chosen order of synchronizing snapshot pairs is based on the creation using the snap-id.

Important

Synchronizing hard links is not supported. Hard linked files get synchronized as regular files.

The CephFS snapshot mirroring includes features, for example snapshot incarnation or high availability. These can be managed through Ceph Manager mirroring module, which is the recommended control interface.

Ceph Manager Module and interfaces

The Ceph Manager mirroring module is disabled by default. It provides interfaces for managing mirroring of directory snapshots. Ceph Manager interfaces are mostly wrappers around monitor commands for managing CephFS mirroring. They are the recommended control interface.

The Ceph Manager mirroring module is implemented as a Ceph Manager plugin. It is responsible for assigning directories to the cephfs-mirror daemons for synchronization.

The Ceph Manager mirroring module also provides a family of commands to control mirroring of directory snapshots. The mirroring module does not manage the cephfs-mirror daemons. The stopping, starting, restarting, and enabling of the cephfs-mirror daemons is controlled by systemctl, but managed by cephadm.

Note

Mirroring module commands use the fs snapshot mirror prefix as compared to the monitor commands with the fs mirror prefix. Assure that you are using the module command prefix to control the mirroring of directory snapshots.

Snapshot incarnation

A snapshot might be deleted and recreated with the same name and different content. The user could synchronize an "old" snapshot earlier and recreate the snapshot when the mirroring was disabled. Using snapshot names to infer the point-of-continuation would result in the “new” snapshot, an incarnation, never getting picked up for synchronization.

Snapshots on the secondary file system store the snap-id of the snapshot it was synchronized from. This metadata is stored in the SnapInfo structure on the Ceph Metadata Server.

High availability

You can deploy multiple cephfs-mirror daemons on two or more nodes to achieve concurrency in synchronization of directory snapshots. When cephfs-mirror daemons are deployed or terminated, the Ceph Manager mirroring module discovers the modified set of cephfs-mirror daemons and rebalances the directory assignment amongst the new set thus providing high availability.

cephfs-mirror daemons share the synchronization load using a simple M/N policy, where M is the number of directories and N is the number of cephfs-mirror daemons.

Re-addition of Ceph File System mirror peers

When re-adding or reassigning a peer to a CephFS in another cluster, ensure that all mirror daemons have stopped synchronization to the peer. You can verify this with the fs mirror status command. The Peer UUID should not show up in the command output.

Purge synchronized directories from the peer before re-adding it to another CephFS, especially those directories which might exist in the new primary file system. This is not required if you are re-adding a peer to the same primary file system it was earlier synchronized from.

You can configure a Ceph File System (CephFS) for mirroring to replicate snapshots to another CephFS on a remote Red Hat Ceph Storage cluster.

Note

The time taken for synchronizing to a remote storage cluster depends on the file size and the total number of files in the mirroring path.

Prerequisites

  • The source and the target storage clusters must be healthy and running Red Hat Ceph Storage 7.0 or later.
  • Root-level access to a Ceph Monitor node in the source and the target storage clusters.
  • At least one Ceph File System deployed on your storage cluster.

Procedure

  1. Log into the Cephadm shell:

    Example

    [root@host01 ~]# cephadm shell
    Copy to Clipboard Toggle word wrap

  2. On the source storage cluster, deploy the CephFS mirroring daemon:

    Syntax

    ceph orch apply cephfs-mirror ["NODE_NAME"]
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph orch apply cephfs-mirror "node1.example.com"
Scheduled cephfs-mirror update...
    Copy to Clipboard Toggle word wrap

    This command creates a Ceph user called, cephfs-mirror, and deploys the cephfs-mirror daemon on the given node.

    1. Optional: Deploy multiple CephFS mirroring daemons and achieve high availability:

      Syntax

      ceph orch apply cephfs-mirror --placement="PLACEMENT_SPECIFICATION"
      Copy to Clipboard Toggle word wrap

      Example

      [ceph: root@host01 /]# ceph orch apply cephfs-mirror --placement="3 host1 host2 host3"
Scheduled cephfs-mirror update...
      Copy to Clipboard Toggle word wrap

      This example deploys three cephfs-mirror daemons on different hosts.

      Warning

      Do not separate the hosts with commas as it results in the following error: 

      Error EINVAL: name component must include only a-z, 0-9, and -
      Copy to Clipboard Toggle word wrap

  3. On the target storage cluster, create a user for each CephFS peer:

    Syntax

    ceph fs authorize FILE_SYSTEM_NAME CLIENT_NAME / rwps
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs authorize cephfs client.mirror_remote / rwps
[client.mirror_remote]
        key = AQCjZ5Jg739AAxAAxduIKoTZbiFJ0lgose8luQ==
    Copy to Clipboard Toggle word wrap

  4. On the source storage cluster, enable the CephFS mirroring module:

    Example

    [ceph: root@host01 /]# ceph mgr module enable mirroring
    Copy to Clipboard Toggle word wrap

  5. On the source storage cluster, enable mirroring on a Ceph File System:

    Syntax

    ceph fs snapshot mirror enable FILE_SYSTEM_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs snapshot mirror enable cephfs
    Copy to Clipboard Toggle word wrap

    1. Optional: Disable snapshot mirroring:

      Syntax

      ceph fs snapshot mirror disable FILE_SYSTEM_NAME
      Copy to Clipboard Toggle word wrap

      Example

      [ceph: root@host01 /]# ceph fs snapshot mirror disable cephfs
      Copy to Clipboard Toggle word wrap

      Warning

      Disabling snapshot mirroring on a file system removes the configured peers. You have to import the peers again by bootstrapping them.

  6. Prepare the target peer storage cluster.

    1. On a target node, enable the mirroring Ceph Manager module:

      Example

      [ceph: root@host01 /]# ceph mgr module enable mirroring
      Copy to Clipboard Toggle word wrap

    2. On the same target node, create the peer bootstrap:

      Syntax

      ceph fs snapshot mirror peer_bootstrap create FILE_SYSTEM_NAME CLIENT_NAME SITE_NAME
      Copy to Clipboard Toggle word wrap

      The SITE_NAME is a user-defined string to identify the target storage cluster.

      Example

      [ceph: root@host01 /]# ceph fs snapshot mirror peer_bootstrap create cephfs client.mirror_remote remote-site
{"token": "eyJmc2lkIjogIjBkZjE3MjE3LWRmY2QtNDAzMC05MDc5LTM2Nzk4NTVkNDJlZiIsICJmaWxlc3lzdGVtIjogImJhY2t1cF9mcyIsICJ1c2VyIjogImNsaWVudC5taXJyb3JfcGVlcl9ib290c3RyYXAiLCAic2l0ZV9uYW1lIjogInNpdGUtcmVtb3RlIiwgImtleSI6ICJBUUFhcDBCZ0xtRmpOeEFBVnNyZXozai9YYUV0T2UrbUJEZlJDZz09IiwgIm1vbl9ob3N0IjogIlt2MjoxOTIuMTY4LjAuNTo0MDkxOCx2MToxOTIuMTY4LjAuNTo0MDkxOV0ifQ=="}
      Copy to Clipboard Toggle word wrap

      Copy the token string between the double quotes for use in the next step.

  7. On the source storage cluster, import the bootstrap token from the target storage cluster:

    Syntax

    ceph fs snapshot mirror peer_bootstrap import FILE_SYSTEM_NAME TOKEN
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs snapshot mirror peer_bootstrap import cephfs eyJmc2lkIjogIjBkZjE3MjE3LWRmY2QtNDAzMC05MDc5LTM2Nzk4NTVkNDJlZiIsICJmaWxlc3lzdGVtIjogImJhY2t1cF9mcyIsICJ1c2VyIjogImNsaWVudC5taXJyb3JfcGVlcl9ib290c3RyYXAiLCAic2l0ZV9uYW1lIjogInNpdGUtcmVtb3RlIiwgImtleSI6ICJBUUFhcDBCZ0xtRmpOeEFBVnNyZXozai9YYUV0T2UrbUJEZlJDZz09IiwgIm1vbl9ob3N0IjogIlt2MjoxOTIuMTY4LjAuNTo0MDkxOCx2MToxOTIuMTY4LjAuNTo0MDkxOV0ifQ==
    Copy to Clipboard Toggle word wrap

  8. On the source storage cluster, list the CephFS mirror peers:

    Syntax

    ceph fs snapshot mirror peer_list FILE_SYSTEM_NAME
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs snapshot mirror peer_list cephfs
{"e5ecb883-097d-492d-b026-a585d1d7da79": {"client_name": "client.mirror_remote", "site_name": "remote-site", "fs_name": "cephfs", "mon_host": "[v2:10.0.211.54:3300/0,v1:10.0.211.54:6789/0] [v2:10.0.210.56:3300/0,v1:10.0.210.56:6789/0] [v2:10.0.210.65:3300/0,v1:10.0.210.65:6789/0]"}}
    Copy to Clipboard Toggle word wrap

    1. Optional: Remove a snapshot peer:

      Syntax

      ceph fs snapshot mirror peer_remove FILE_SYSTEM_NAME PEER_UUID
      Copy to Clipboard Toggle word wrap

      Example

      [ceph: root@host01 /]# ceph fs snapshot mirror peer_remove cephfs e5ecb883-097d-492d-b026-a585d1d7da79
      Copy to Clipboard Toggle word wrap

      Note

      See Viewing the mirror status for a Ceph File System on how to find the peer UUID value.

  9. On the source storage cluster, configure a directory for snapshot mirroring:

    Syntax

    ceph fs snapshot mirror add FILE_SYSTEM_NAME PATH
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs snapshot mirror add cephfs /volumes/_nogroup/subvol_1
    Copy to Clipboard Toggle word wrap

    Important

    Only absolute paths inside the Ceph File System are valid.

    Note

    The Ceph Manager mirroring module normalizes the path. For example, the /d1/d2/../dN directories are equivalent to /d1/d2. Once a directory has been added for mirroring, its ancestor directories and subdirectories are prevented from being added for mirroring.

    1. Optional: Stop snapshot mirroring for a directory:

      Syntax

      ceph fs snapshot mirror remove FILE_SYSTEM_NAME PATH
      Copy to Clipboard Toggle word wrap

      Example

      [ceph: root@host01 /]# ceph fs snapshot mirror remove cephfs /home/user1
      Copy to Clipboard Toggle word wrap

The Ceph File System (CephFS) mirror daemon (cephfs-mirror) gets asynchronous notifications about changes in the CephFS mirroring status, along with peer updates. The CephFS mirroring module provides a mirror daemon status interface to check mirror daemon status. For more detailed information, you can query the cephfs-mirror admin socket with commands to retrieve the mirror status and peer status.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • At least one deployment of a Ceph File System with mirroring enabled.
  • Root-level access to the node running the CephFS mirroring daemon.

Procedure

  1. Log into the Cephadm shell:

    Example

    [root@host01 ~]# cephadm shell
    Copy to Clipboard Toggle word wrap

  2. Check the cephfs-mirror daemon status:

    Syntax

    ceph fs snapshot mirror daemon status
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs snapshot mirror daemon status
[
  {
    "daemon_id": 15594,
    "filesystems": [
      {
        "filesystem_id": 1,
        "name": "cephfs",
        "directory_count": 1,
        "peers": [
          {
            "uuid": "e5ecb883-097d-492d-b026-a585d1d7da79",
            "remote": {
              "client_name": "client.mirror_remote",
              "cluster_name": "remote-site",
              "fs_name": "cephfs"
            },
            "stats": {
              "failure_count": 1,
              "recovery_count": 0
            }
          }
        ]
      }
    ]
  }
]
    Copy to Clipboard Toggle word wrap

    For more detailed information, use the admin socket interface as detailed below.

  3. Find the Ceph File System ID on the node running the CephFS mirroring daemon:

    Syntax

    ceph --admin-daemon PATH_TO_THE_ASOK_FILE help
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph --admin-daemon /var/run/ceph/1011435c-9e30-4db6-b720-5bf482006e0e/ceph-client.cephfs-mirror.node1.bndvox.asok help
{
    ...
    "fs mirror peer status cephfs@11 1011435c-9e30-4db6-b720-5bf482006e0e": "get peer mirror status",
    "fs mirror status cephfs@11": "get filesystem mirror status",
    ...
}
    Copy to Clipboard Toggle word wrap

    The Ceph File System ID in this example is cephfs@11.

    Note

    When mirroring is disabled, the respective fs mirror status command for the file system does not show up in the help command.

  4. View the mirror status:

    Syntax

    ceph --admin-daemon PATH_TO_THE_ASOK_FILE fs mirror status FILE_SYSTEM_NAME@_FILE_SYSTEM_ID
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph --admin-daemon /var/run/ceph/1011435c-9e30-4db6-b720-5bf482006e0e/ceph-client.cephfs-mirror.node1.bndvox.asok fs mirror status cephfs@11
{
  "rados_inst": "192.168.0.5:0/1476644347",
  "peers": {
      "1011435c-9e30-4db6-b720-5bf482006e0e": {
    1 
    
          "remote": {
              "client_name": "client.mirror_remote",
              "cluster_name": "remote-site",
              "fs_name": "cephfs"
          }
      }
  },
  "snap_dirs": {
      "dir_count": 1
  }
}
    Copy to Clipboard Toggle word wrap

    1
    This is the unique peer UUID.

  5. View the peer status:

    Syntax

    ceph --admin-daemon PATH_TO_ADMIN_SOCKET fs mirror status FILE_SYSTEM_NAME@FILE_SYSTEM_ID PEER_UUID
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph --admin-daemon /var/run/ceph/cephfs-mirror.asok fs mirror peer status cephfs@11 1011435c-9e30-4db6-b720-5bf482006e0e
{
  "/home/user1": {
      "state": "idle",
    1 
    
      "last_synced_snap": {
          "id": 120,
          "name": "snap1",
          "sync_duration": 0.079997898999999997,
          "sync_time_stamp": "274900.558797s"
      },
      "snaps_synced": 2,
    2 
    
      "snaps_deleted": 0,
    3 
    
      "snaps_renamed": 0
  }
}
    Copy to Clipboard Toggle word wrap

    The state can be one of these three values:

    1
    idle means the directory is currently not being synchronized.
    2
    syncing means the directory is currently being synchronized.
    3
    failed means the directory has hit the upper limit of consecutive failures.

The default number of consecutive failures is 10, and the default retry interval is 60 seconds.

  1. Display the directory to which cephfs-mirror daemon is mapped:

    Syntax

    ceph fs snapshot mirror dirmap FILE_SYSTEM_NAME PATH
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@host01 /]# ceph fs snapshot mirror dirmap cephfs /volumes/_nogroup/subvol_1
{
  "instance_id": "25184",
    1 
    
  "last_shuffled": 1661162007.012663,
  "state": "mapped"
}
    Copy to Clipboard Toggle word wrap

    1
    instance_id is the RADOS instance-ID associated with a cephfs-mirror daemon.

    Example

    [ceph: root@host01 /]# ceph fs snapshot mirror dirmap cephfs /volumes/_nogroup/subvol_1
{
  "reason": "no mirror daemons running",
  "state": "stalled"
    1 
    
}
    Copy to Clipboard Toggle word wrap

    1
    stalled state means the CephFS mirroring is stalled.

    The second example shows the command output when no mirror daemons are running.

Viewing these metrics helps in monitoring the performance and the sync progress. Check Ceph File System snapshot mirror health and volume metrics by using the counter dump.

Prerequistes

  • A running IBM Storage Ceph cluster.
  • A minimum of one deployment of a Ceph File System snapshot mirroring enabled.
  • Root-level access to the node running the Ceph File System mirroring daemon.

Procedure

  1. Get the name of the asok file. The asok file is available where the mirroring daemon is running and is located at /var/run/ceph/ within the cephadm shell.

  2. Check the mirroring metrics and synchronization status by running the following command on the node running the CephFS mirroring daemon.

    Syntax

    [ceph: root@mirror-host01 /]# ceph --admin-daemon ASOK_FILE_NAME counter dump
    Copy to Clipboard Toggle word wrap

    Example

    [ceph: root@mirror-host01 /]# ceph --admin-daemon ceph-client.cephfs-mirror.ceph1-hk-n-0mfqao-node7.pnbrlu.2.93909288073464.asok counter dump

[
  {
    "key": "cephfs_mirror",
    "value": [
      {
        "labels": {},
        "counters": {
          "mirrored_filesystems": 1,
          "mirror_enable_failures": 0
        }
      }
    ]
  },
  {
    "key": "cephfs_mirror_mirrored_filesystems",
    "value": [
      {
        "labels": {
          "filesystem": "cephfs"
        },
        "counters": {
          "mirroring_peers": 1,
          "directory_count": 1
        }
      }
    ]
  },
  {
    "key": "cephfs_mirror_peers",
    "value": [
      {
        "labels": {
          "peer_cluster_filesystem": "cephfs",
          "peer_cluster_name": "remote_site",
          "source_filesystem": "cephfs",
          "source_fscid": "1"
        },
        "counters": {
          "snaps_synced": 1,
          "snaps_deleted": 0,
          "snaps_renamed": 0,
          "sync_failures": 0,
          "avg_sync_time": {
            "avgcount": 1,
            "sum": 4.216959457,
            "avgtime": 4.216959457
          },
          "sync_bytes": 132
        }
      }
    ]
  }
]
    Copy to Clipboard Toggle word wrap

Metrics description:

Labeled Perf Counters generate metrics which can be consumed by the OCP/ODF dashboard to provide monitoring of geo-replication in the OCP and ACM dashboard and elsewhere.

This would generate the progress of cephfs_mirror syncing and provide monitoring capability. The exported metrics enable monitoring based on the following alerts.

mirroring_peers
The number of peers involved in mirroring.
directory_count
The total number of directories being synchronized.
mirrored_filesystems
The total number of file systems which are mirrored.
mirror_enable_failures
Enable mirroring failures.
snaps_synced
The total number of snapshots successfully synchronized.
sync_bytes
The total bytes being synchronized
sync_failures
The total number of failed snapshot synchronizations.
snaps_deleted
The total number of snapshots deleted.
snaps_renamed
The total number of snapshots renamed.
avg_synced_time
The average time taken by all snapshot synchronizations.
last_synced_start
The sync start time of the last synced snapshot.
last_synced_end
The sync end time of the last synced snapshot.
last_synced_duration
The time duration of the last synchronization.
last_synced_bytes
The total bytes being synchronized for the last synced snapshot.

Cluster health checks

The Ceph Monitor daemons generate health messages in response to certain states of the Metadata Server (MDS). Below is the list of the health messages and their explanation:

mds rank(s) <ranks> have failed
One or more MDS ranks are not currently assigned to any MDS daemon. The storage cluster will not recover until a suitable replacement daemon starts.
mds rank(s) <ranks> are damaged
One or more MDS ranks has encountered severe damage to its stored metadata, and cannot start again until the metadata is repaired.
mds cluster is degraded
One or more MDS ranks are not currently up and running, clients might pause metadata I/O until this situation is resolved. This includes ranks being failed or damaged, and includes ranks which are running on an MDS but are not in the active state yet — for example, ranks in the replay state.
mds <names> are laggy
The MDS daemons are supposed to send beacon messages to the monitor in an interval specified by the mds_beacon_interval option, the default is 4 seconds. If an MDS daemon fails to send a message within the time specified by the mds_beacon_grace option, the default is 15 seconds. The Ceph Monitor marks the MDS daemon as laggy and automatically replaces it with a standby daemon if any is available.

Daemon-reported health checks

The MDS daemons can identify a variety of unwanted conditions, and return them in the output of the ceph status command. These conditions have human readable messages, and also have a unique code starting MDS_HEALTH, which appears in JSON output. Below is the list of the daemon messages, their codes, and explanation.

"Behind on trimming…​"

Code: MDS_HEALTH_TRIM

CephFS maintains a metadata journal that is divided into log segments. The length of journal (in number of segments) is controlled by the mds_log_max_segments setting. When the number of segments exceeds that setting, the MDS starts writing back metadata so that it can remove (trim) the oldest segments. If this process is too slow, or a software bug is preventing trimming, then this health message appears. The threshold for this message to appear is for the number of segments to be double mds_log_max_segments.

Note

Increasing mds_log_max_segments is recommended if the trim warning is encountered. However, ensure that this configuration is reset back to its default when the cluster health recovers and the trim warning is seen no more. It is recommended to set mds_log_max_segments to 256 to allow the MDS to catch up with trimming.

"Client <name> failing to respond to capability release"

Code: MDS_HEALTH_CLIENT_LATE_RELEASE, MDS_HEALTH_CLIENT_LATE_RELEASE_MANY

CephFS clients are issued capabilities by the MDS. The capabilities work like locks. Sometimes, for example, when another client needs access, the MDS requests clients to release their capabilities. If the client is unresponsive, it might fail to do so promptly, or fail to do so at all. This message appears if a client has taken a longer time to comply than the time specified by the mds_revoke_cap_timeout option (default is 60 seconds).

"Client <name> failing to respond to cache pressure"

Code: MDS_HEALTH_CLIENT_RECALL, MDS_HEALTH_CLIENT_RECALL_MANY

Clients maintain a metadata cache. Items, such as inodes, in the client cache, are also pinned in the MDS cache. When the MDS needs to shrink its cache to stay within its own cache size limits, the MDS sends messages to clients to shrink their caches too. If a client is unresponsive, it can prevent the MDS from properly staying within its cache size, and the MDS might eventually run out of memory and terminate unexpectedly. This message appears if a client has taken more time to comply than the time specified by the mds_recall_state_timeout option (default is 60 seconds). See Metadata Server cache size limits section for details.

"Client name failing to advance its oldest client/flush tid"

Code: MDS_HEALTH_CLIENT_OLDEST_TID, MDS_HEALTH_CLIENT_OLDEST_TID_MANY

The CephFS protocol for communicating between clients and MDS servers uses a field called oldest tid to inform the MDS of which client requests are fully complete so that the MDS can forget about them. If an unresponsive client is failing to advance this field, the MDS might be prevented from properly cleaning up resources used by client requests. This message appears if a client has more requests than the number specified by the max_completed_requests option (default is 100000) that are complete on the MDS side but have not yet been accounted for in the client’s oldest tid value.

"Metadata damage detected"

Code: MDS_HEALTH_DAMAGE

Corrupt or missing metadata was encountered when reading from the metadata pool. This message indicates that the damage was sufficiently isolated for the MDS to continue operating, although client accesses to the damaged subtree return I/O errors. Use the damage ls administration socket command to view details on the damage. This message appears as soon as any damage is encountered.

"MDS in read-only mode"

Code: MDS_HEALTH_READ_ONLY

The MDS has entered into read-only mode and will return the EROFS error codes to client operations that attempt to modify any metadata. The MDS enters into read-only mode:

  • If it encounters a write error while writing to the metadata pool.
  • If the administrator forces the MDS to enter into read-only mode by using the force_readonly administration socket command.
"<N> slow requests are blocked"

Code: MDS_HEALTH_SLOW_REQUEST

One or more client requests have not been completed promptly, indicating that the MDS is either running very slowly, or encountering a bug. Use the ops administration socket command to list outstanding metadata operations. This message appears if any client requests have taken more time than the value specified by the mds_op_complaint_time option (default is 30 seconds).

"Too many inodes in cache"
Code: MDS_HEALTH_CACHE_OVERSIZED

The MDS has failed to trim its cache to comply with the limit set by the administrator. If the MDS cache becomes too large, the daemon might exhaust available memory and terminate unexpectedly. By default, this message appears if the MDS cache size is 50% greater than its limit.

Additional Resources

Refer to this list of commands that can be used for the Metadata Server (MDS) daemon configuration.

mon_force_standby_active
Description
If set to true, monitors force MDS in standby replay mode to be active. Set under the [mon] or [global] section in the Ceph configuration file.
Type
Boolean
Default
true
max_mds
Description
The number of active MDS daemons during cluster creation. Set under the [mon] or [global] section in the Ceph configuration file.
Type
32-bit Integer
Default
1
mds_cache_memory_limit
Description
The memory limit the MDS enforces for its cache. Red Hat recommends using this parameter instead of the mds cache size parameter.
Type
64-bit Integer Unsigned
Default
4294967296
mds_cache_reservation
Description
The cache reservation, memory or inodes, for the MDS cache to maintain. The value is a percentage of the maximum cache configured. Once the MDS begins dipping into its reservation, it recalls client state until its cache size shrinks to restore the reservation.
Type
Float
Default
0.05
mds_cache_size
Description
The number of inodes to cache. A value of 0 indicates an unlimited number. Red Hat recommends to use the mds_cache_memory_limit to limit the amount of memory the MDS cache uses.
Type
32-bit Integer
Default
0
mds_cache_mid
Description
The insertion point for new items in the cache LRU, from the top.
Type
Float
Default
0.7
mds_dir_commit_ratio
Description
The fraction of directory that contains erroneous information before Ceph commits using a full update instead of partial update.
Type
Float
Default
0.5
mds_dir_max_commit_size
Description
The maximum size of a directory update in MB before Ceph breaks the directory into smaller transactions.
Type
32-bit Integer
Default
90
mds_decay_halflife
Description
The half-life of the MDS cache temperature.
Type
Float
Default
5
mds_beacon_interval
Description
The frequency, in seconds, of beacon messages sent to the monitor.
Type
Float
Default
4
mds_beacon_grace
Description
The interval without beacons before Ceph declares a MDS laggy and possibly replaces it.
Type
Float
Default
15
mds_blacklist_interval
Description
The blacklist duration for failed MDS daemons in the OSD map.
Type
Float
Default
24.0*60.0
mds_session_timeout
Description
The interval, in seconds, of client inactivity before Ceph times out capabilities and leases.
Type
Float
Default
60
mds_session_autoclose
Description
The interval, in seconds, before Ceph closes a laggy client’s session.
Type
Float
Default
300
mds_reconnect_timeout
Description
The interval, in seconds, to wait for clients to reconnect during a MDS restart.
Type
Float
Default
45
mds_tick_interval
Description
How frequently the MDS performs internal periodic tasks.
Type
Float
Default
5
mds_dirstat_min_interval
Description
The minimum interval, in seconds, to try to avoid propagating recursive statistics up the tree.
Type
Float
Default
1
mds_scatter_nudge_interval
Description
How quickly changes in directory statistics propagate up.
Type
Float
Default
5
mds_client_prealloc_inos
Description
The number of inode numbers to preallocate per client session.
Type
32-bit Integer
Default
1000
mds_early_reply
Description
Determines whether the MDS allows clients to see request results before they commit to the journal.
Type
Boolean
Default
true
mds_use_tmap
Description
Use trivialmap for directory updates.
Type
Boolean
Default
true
mds_default_dir_hash
Description
The function to use for hashing files across directory fragments.
Type
32-bit Integer
Default
2,that is, rjenkins
mds_log
Description
Set to true if the MDS should journal metadata updates. Disable for benchmarking only.
Type
Boolean
Default
true
mds_log_skip_corrupt_events
Description
Determines whether the MDS tries to skip corrupt journal events during journal replay.
Type
Boolean
Default
false
mds_log_max_events
Description
The maximum events in the journal before Ceph initiates trimming. Set to -1 to disable limits.
Type
32-bit Integer
Default
-1
mds_log_max_segments
Description
The maximum number of segments or objects in the journal before Ceph initiates trimming. Set to -1 to disable limits.
Type
32-bit Integer
Default
30
mds_log_max_expiring
Description
The maximum number of segments to expire in parallels.
Type
32-bit Integer
Default
20
mds_log_eopen_size
Description
The maximum number of inodes in an EOpen event.
Type
32-bit Integer
Default
100
mds_bal_sample_interval
Description
Determines how frequently to sample directory temperature when making fragmentation decisions.
Type
Float
Default
3
mds_bal_replicate_threshold
Description
The maximum temperature before Ceph attempts to replicate metadata to other nodes.
Type
Float
Default
8000
mds_bal_unreplicate_threshold
Description
The minimum temperature before Ceph stops replicating metadata to other nodes.
Type
Float
Default
0
mds_bal_frag
Description
Determines whether or not the MDS fragments directories.
Type
Boolean
Default
false
mds_bal_split_size
Description
The maximum directory size before the MDS splits a directory fragment into smaller bits. The root directory has a default fragment size limit of 10000.
Type
32-bit Integer
Default
10000
mds_bal_split_rd
Description
The maximum directory read temperature before Ceph splits a directory fragment.
Type
Float
Default
25000
mds_bal_split_wr
Description
The maximum directory write temperature before Ceph splits a directory fragment.
Type
Float
Default
10000
mds_bal_split_bits
Description
The number of bits by which to split a directory fragment.
Type
32-bit Integer
Default
3
mds_bal_merge_size
Description
The minimum directory size before Ceph tries to merge adjacent directory fragments.
Type
32-bit Integer
Default
50
mds_bal_merge_rd
Description
The minimum read temperature before Ceph merges adjacent directory fragments.
Type
Float
Default
1000
mds_bal_merge_wr
Description
The minimum write temperature before Ceph merges adjacent directory fragments.
Type
Float
Default
1000
mds_bal_interval
Description
The frequency, in seconds, of workload exchanges between MDS nodes.
Type
32-bit Integer
Default
10
mds_bal_fragment_interval
Description
The frequency, in seconds, of adjusting directory fragmentation.
Type
32-bit Integer
Default
5
mds_bal_idle_threshold
Description
The minimum temperature before Ceph migrates a subtree back to its parent.
Type
Float
Default
0
mds_bal_max
Description
The number of iterations to run balancer before Ceph stops. For testing purposes only.
Type
32-bit Integer
Default
-1
mds_bal_max_until
Description
The number of seconds to run balancer before Ceph stops. For testing purposes only.
Type
32-bit Integer
Default
-1
mds_bal_mode
Description

The method for calculating MDS load:

  • 1 = Hybrid.
  • 2 = Request rate and latency.
  • 3 = CPU load.
Type
32-bit Integer
Default
0
mds_bal_min_rebalance
Description
The minimum subtree temperature before Ceph migrates.
Type
Float
Default
0.1
mds_bal_min_start
Description
The minimum subtree temperature before Ceph searches a subtree.
Type
Float
Default
0.2
mds_bal_need_min
Description
The minimum fraction of target subtree size to accept.
Type
Float
Default
0.8
mds_bal_need_max
Description
The maximum fraction of target subtree size to accept.
Type
Float
Default
1.2
mds_bal_midchunk
Description
Ceph migrates any subtree that is larger than this fraction of the target subtree size.
Type
Float
Default
0.3
mds_bal_minchunk
Description
Ceph ignores any subtree that is smaller than this fraction of the target subtree size.
Type
Float
Default
0.001
mds_bal_target_removal_min
Description
The minimum number of balancer iterations before Ceph removes an old MDS target from the MDS map.
Type
32-bit Integer
Default
5
mds_bal_target_removal_max
Description
The maximum number of balancer iterations before Ceph removes an old MDS target from the MDS map.
Type
32-bit Integer
Default
10
mds_replay_interval
Description
The journal poll interval when in standby-replay mode for a hot standby.
Type
Float
Default
1
mds_shutdown_check
Description
The interval for polling the cache during MDS shutdown.
Type
32-bit Integer
Default
0
mds_thrash_exports
Description
Ceph randomly exports subtrees between nodes. For testing purposes only.
Type
32-bit Integer
Default
0
mds_thrash_fragments
Description
Ceph randomly fragments or merges directories.
Type
32-bit Integer
Default
0
mds_dump_cache_on_map
Description
Ceph dumps the MDS cache contents to a file on each MDS map.
Type
Boolean
Default
false
mds_dump_cache_after_rejoin
Description
Ceph dumps MDS cache contents to a file after rejoining the cache during recovery.
Type
Boolean
Default
false
mds_verify_scatter
Description
Ceph asserts that various scatter/gather invariants are true. For developer use only.
Type
Boolean
Default
false
mds_debug_scatterstat
Description
Ceph asserts that various recursive statistics invariants are true. For developer use only.
Type
Boolean
Default
false
mds_debug_frag
Description
Ceph verifies directory fragmentation invariants when convenient. For developer use only.
Type
Boolean
Default
false
mds_debug_auth_pins
Description
The debug authentication pin invariants. For developer use only.
Type
Boolean
Default
false
mds_debug_subtrees
Description
Debugging subtree invariants. For developer use only.
Type
Boolean
Default
false
mds_kill_mdstable_at
Description
Ceph injects a MDS failure in a MDS Table code. For developer use only.
Type
32-bit Integer
Default
0
mds_kill_export_at
Description
Ceph injects a MDS failure in the subtree export code. For developer use only.
Type
32-bit Integer
Default
0
mds_kill_import_at
Description
Ceph injects a MDS failure in the subtree import code. For developer use only.
Type
32-bit Integer
Default
0
mds_kill_link_at
Description
Ceph injects a MDS failure in a hard link code. For developer use only.
Type
32-bit Integer
Default
0
mds_kill_rename_at
Description
Ceph injects a MDS failure in the rename code. For developer use only.
Type
32-bit Integer
Default
0
mds_wipe_sessions
Description
Ceph deletes all client sessions on startup. For testing purposes only.
Type
Boolean
Default
0
mds_wipe_ino_prealloc
Description
Ceph deletes inode preallocation metadata on startup. For testing purposes only.
Type
Boolean
Default
0
mds_skip_ino
Description
The number of inode numbers to skip on startup. For testing purposes only.
Type
32-bit Integer
Default
0
mds_standby_for_name
Description
The MDS daemon is a standby for another MDS daemon of the name specified in this setting.
Type
String
Default
N/A
mds_standby_for_rank
Description
An instance of the MDS daemon is a standby for another MDS daemon instance of this rank.
Type
32-bit Integer
Default
-1
mds_standby_replay
Description
Determines whether the MDS daemon polls and replays the log of an active MDS when used as a hot standby.
Type
Boolean
Default
false

Appendix C. Journaler configuration reference
Copy link

Reference of the list commands that can be used for journaler configuration.

journaler_write_head_interval
Description
How frequently to update the journal head object.
Type
Integer
Required
No
Default
15
journaler_prefetch_periods
Description
How many stripe periods to read ahead on journal replay.
Type
Integer
Required
No
Default
10
journaler_prezero_periods
Description
How many stripe periods to zero ahead of write position.
Type
Integer
Required
No
Default
10
journaler_batch_interval
Description
Maximum additional latency in seconds to incur artificially.
Type
Double
Required
No
Default
.001
journaler_batch_max
Description
Maximum bytes that will be delayed flushing.
Type
64-bit Unsigned Integer
Required
No
Default
0

This section lists configuration options for Ceph File System (CephFS) mirrors.

cephfs_mirror_max_concurrent_directory_syncs
Description
Maximum number of directory snapshots that can be synchronized concurrently by cephfs-mirror daemon. Controls the number of synchronization threads.
Type
Integer
Default
3
Min
1
cephfs_mirror_action_update_interval
Description
Interval in seconds to process pending mirror update actions.
Type
secs
Default
2
Min
1
cephfs_mirror_restart_mirror_on_blocklist_interval
Description
Interval in seconds to restart blocklisted mirror instances. Setting to zero (0) disables restarting blocklisted instances.
Type
secs
Default
30
Min
0
cephfs_mirror_max_snapshot_sync_per_cycle
Description
Maximum number of snapshots to mirror when a directory is picked up for mirroring by worker threads.
Type
Integer
Default
3
Min
1
cephfs_mirror_directory_scan_interval
Description
Interval in seconds to scan configured directories for snapshot mirroring.
Type
Integer
Default
10
Min
1
cephfs_mirror_max_consecutive_failures_per_directory
Description
Number of consecutive snapshot synchronization failures to mark a directory as “failed”. Failed directories are retried for synchronization less frequently.
Type
Integer
Default
10
Min
0
cephfs_mirror_retry_failed_directories_interval
Description
Interval in seconds to retry synchronization for failed directories.
Type
Integer
Default
60
Min
1
cephfs_mirror_restart_mirror_on_failure_interval
Description
Interval in seconds to restart failed mirror instances. Setting to zero (0) disables restarting failed mirror instances.
Type
secs
Default
20
Min
0
cephfs_mirror_mount_timeout
Description
Timeout in seconds for mounting primary or secondary CephFS by the cephfs-mirror daemon. Setting this to a higher value could result in the mirror daemon getting stalled when mounting a file system if the cluster is not reachable. This option is used to override the usual client_mount_timeout.
Type
secs
Default
10
Min
0

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