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Chapter 7. The ceph-volume utility

As a storage administrator, you can prepare, list, create, activate, deactivate, batch, trigger, zap, and migrate Ceph OSDs using the ceph-volume utility. The ceph-volume utility is a single-purpose command-line tool to deploy logical volumes as OSDs. It uses a plugin-type framework to deploy OSDs with different device technologies. The ceph-volume utility follows a similar workflow of the ceph-disk utility for deploying OSDs, with a predictable, and robust way of preparing, activating, and starting OSDs. Currently, the ceph-volume utility only supports the lvm plugin, with the plan to support others technologies in the future.

Important

The ceph-disk command is deprecated.

7.1. Ceph volume lvm plugin

By making use of LVM tags, the lvm sub-command is able to store and re-discover by querying devices associated with OSDs so they can be activated. This includes support for lvm-based technologies like dm-cache as well.

When using ceph-volume, the use of dm-cache is transparent, and treats dm-cache like a logical volume. The performance gains and losses when using dm-cache will depend on the specific workload. Generally, random and sequential reads will see an increase in performance at smaller block sizes. While random and sequential writes will see a decrease in performance at larger block sizes.

To use the LVM plugin, add lvm as a subcommand to the ceph-volume command within the cephadm shell: 

[ceph: root@host01 /]# ceph-volume lvm

Following are the lvm subcommands:

  • prepare - Format an LVM device and associate it with an OSD.
  • activate - Discover and mount the LVM device associated with an OSD ID and start the Ceph OSD.
  • list - List logical volumes and devices associated with Ceph.
  • batch - Automatically size devices for multi-OSD provisioning with minimal interaction.
  • deactivate - Deactivate OSDs.
  • create - Create a new OSD from an LVM device.
  • trigger - A systemd helper to activate an OSD.
  • zap - Removes all data and filesystems from a logical volume or partition.
  • migrate - Migrate BlueFS data from to another LVM device.
  • new-wal - Allocate new WAL volume for the OSD at specified logical volume.
  • new-db - Allocate new DB volume for the OSD at specified logical volume.
Note

Using the create subcommand combines the prepare and activate subcommands into one subcommand.

Additional Resources

  • See the create subcommand section for more details.

7.2. Why does ceph-volume replace ceph-disk?

Up to Red Hat Ceph Storage 4, ceph-disk utility was used to prepare, activate, and create OSDs. Starting with Red Hat Ceph Storage 4, ceph-disk is replaced by the ceph-volume utility that aims to be a single purpose command-line tool to deploy logical volumes as OSDs, while maintaining a similar API to ceph-disk when preparing, activating, and creating OSDs.

How does ceph-volume work?

The ceph-volume is a modular tool that currently supports two ways of provisioning hardware devices, legacy ceph-disk devices and LVM (Logical Volume Manager) devices. The ceph-volume lvm command uses the LVM tags to store information about devices specific to Ceph and its relationship with OSDs. It uses these tags to later re-discover and query devices associated with OSDS so that it can activate them. It supports technologies based on LVM and dm-cache as well.

The ceph-volume utility uses dm-cache transparently and treats it as a logical volume. You might consider the performance gains and losses when using dm-cache, depending on the specific workload you are handling. Generally, the performance of random and sequential read operations increases at smaller block sizes; while the performance of random and sequential write operations decreases at larger block sizes. Using ceph-volume does not introduce any significant performance penalties.

Important

The ceph-disk utility is deprecated.

Note

The ceph-volume simple command can handle legacy ceph-disk devices, if these devices are still in use.

How does ceph-disk work?

The ceph-disk utility was required to support many different types of init systems, such as upstart or sysvinit, while being able to discover devices. For this reason, ceph-disk concentrates only on GUID Partition Table (GPT) partitions. Specifically on GPT GUIDs that label devices in a unique way to answer questions like:

  • Is this device a journal?
  • Is this device an encrypted data partition?
  • Was the device left partially prepared?

To solve these questions, ceph-disk uses UDEV rules to match the GUIDs.

What are disadvantages of using ceph-disk?

Using the UDEV rules to call ceph-disk can lead to a back-and-forth between the ceph-disk systemd unit and the ceph-disk executable. The process is very unreliable and time consuming and can cause OSDs to not come up at all during the boot process of a node. Moreover, it is hard to debug, or even replicate these problems given the asynchronous behavior of UDEV.

Because ceph-disk works with GPT partitions exclusively, it cannot support other technologies, such as Logical Volume Manager (LVM) volumes, or similar device mapper devices.

To ensure the GPT partitions work correctly with the device discovery workflow, ceph-disk requires a large number of special flags to be used. In addition, these partitions require devices to be exclusively owned by Ceph.

7.3. Preparing Ceph OSDs using ceph-volume

The prepare subcommand prepares an OSD back-end object store and consumes logical volumes (LV) for both the OSD data and journal. It does not modify the logical volumes, except for adding some extra metadata tags using LVM. These tags make volumes easier to discover, and they also identify the volumes as part of the Ceph Storage Cluster and the roles of those volumes in the storage cluster.

The BlueStore OSD backend supports the following configurations:

  • A block device, a block.wal device, and a block.db device
  • A block device and a block.wal device
  • A block device and a block.db device
  • A single block device

The prepare subcommand accepts a whole device or partition, or a logical volume for block.

Prerequisites

  • Root-level access to the OSD nodes.
  • Optionally, create logical volumes. If you provide a path to a physical device, the subcommand turns the device into a logical volume. This approach is simpler, but you cannot configure or change the way the logical volume is created.

Procedure

  1. Extract the Ceph keyring:

    Syntax

    ceph auth get client.ID -o ceph.client.ID.keyring

    Example

    [ceph: root@host01 /]# ceph auth get client.bootstrap-osd -o /var/lib/ceph/bootstrap-osd/ceph.keyring

  2. Prepare the LVM volumes:

    Syntax

    ceph-volume lvm prepare --bluestore --data VOLUME_GROUP/LOGICAL_VOLUME

    Example

    [ceph: root@host01 /]# ceph-volume lvm prepare --bluestore --data example_vg/data_lv

    1. Optionally, if you want to use a separate device for RocksDB, specify the --block.db and --block.wal options:

      Syntax

      ceph-volume lvm prepare --bluestore --block.db BLOCK_DB_DEVICE --block.wal BLOCK_WAL_DEVICE --data DATA_DEVICE

      Example

      [ceph: root@host01 /]# ceph-volume lvm prepare --bluestore --block.db /dev/sda --block.wal /dev/sdb --data /dev/sdc

    2. Optionally, to encrypt data, use the --dmcrypt flag:

      Syntax

      ceph-volume lvm prepare --bluestore --dmcrypt --data VOLUME_GROUP/LOGICAL_VOLUME

      Example

      [ceph: root@host01 /]# ceph-volume lvm prepare --bluestore --dmcrypt --data example_vg/data_lv

Additional Resources

7.4. Listing devices using ceph-volume

You can use the ceph-volume lvm list subcommand to list logical volumes and devices associated with a Ceph cluster, as long as they contain enough metadata to allow for that discovery. The output is grouped by the OSD ID associated with the devices. For logical volumes, the devices key is populated with the physical devices associated with the logical volume.

In some cases, the output of the ceph -s command shows the following error message: 

1 devices have fault light turned on

In such cases, you can list the devices with ceph device ls-lights command which gives the details about the lights on the devices. Based on the information, you can turn off the lights on the devices.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the Ceph OSD node.

Procedure

  • List the devices in the Ceph cluster:

    Example

    [ceph: root@host01 /]# ceph-volume lvm list


====== osd.6 =======

  [block]       /dev/ceph-83909f70-95e9-4273-880e-5851612cbe53/osd-block-7ce687d9-07e7-4f8f-a34e-d1b0efb89920

      block device              /dev/ceph-83909f70-95e9-4273-880e-5851612cbe53/osd-block-7ce687d9-07e7-4f8f-a34e-d1b0efb89920
      block uuid                4d7gzX-Nzxp-UUG0-bNxQ-Jacr-l0mP-IPD8cX
      cephx lockbox secret
      cluster fsid              1ca9f6a8-d036-11ec-8263-fa163ee967ad
      cluster name              ceph
      crush device class        None
      encrypted                 0
      osd fsid                  7ce687d9-07e7-4f8f-a34e-d1b0efb89920
      osd id                    6
      osdspec affinity          all-available-devices
      type                      block
      vdo                       0
      devices                   /dev/vdc

  • Optional: List the devices in the storage cluster with the lights:

    Example

    [ceph: root@host01 /]# ceph device ls-lights

{
    "fault": [
        "SEAGATE_ST12000NM002G_ZL2KTGCK0000C149"
    ],
    "ident": []
}

    1. Optional: Turn off the lights on the device:

      Syntax

      ceph device light off DEVICE_NAME FAULT/INDENT --force

      Example

      [ceph: root@host01 /]# ceph device light off SEAGATE_ST12000NM002G_ZL2KTGCK0000C149 fault --force

7.5. Activating Ceph OSDs using ceph-volume

The activation process enables a systemd unit at boot time, which allows the correct OSD identifier and its UUID to be enabled and mounted.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the Ceph OSD node.
  • Ceph OSDs prepared by the ceph-volume utility.

Procedure

  1. Get the OSD ID and OSD FSID from an OSD node: 

    [ceph: root@host01 /]# ceph-volume lvm list

  2. Activate the OSD:

    Syntax

    ceph-volume lvm activate --bluestore OSD_ID OSD_FSID

    Example

    [ceph: root@host01 /]# ceph-volume lvm activate --bluestore 10 7ce687d9-07e7-4f8f-a34e-d1b0efb89920

    To activate all OSDs that are prepared for activation, use the --all option:

    Example

    [ceph: root@host01 /]# ceph-volume lvm activate --all

  3. Optionally, you can use the trigger subcommand. This command cannot be used directly, and it is used by systemd so that it proxies input to ceph-volume lvm activate. This parses the metadata coming from systemd and startup, detecting the UUID and ID associated with an OSD.

    Syntax

    ceph-volume lvm trigger SYSTEMD_DATA

    Here the SYSTEMD_DATA is in OSD_ID-OSD_FSID format.

    Example

    [ceph: root@host01 /]# ceph-volume lvm trigger 10 7ce687d9-07e7-4f8f-a34e-d1b0efb89920

Additional Resources

7.6. Deactivating Ceph OSDs using ceph-volume

You can deactivate the Ceph OSDs using the ceph-volume lvm subcommand. This subcommand removes the volume groups and the logical volume.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the Ceph OSD node.
  • The Ceph OSDs are activated using the ceph-volume utility.

Procedure

  1. Get the OSD ID from the OSD node: 

    [ceph: root@host01 /]# ceph-volume lvm list

  2. Deactivate the OSD:

    Syntax

    ceph-volume lvm deactivate OSD_ID

    Example

    [ceph: root@host01 /]# ceph-volume lvm deactivate 16

Additional Resources

7.7. Creating Ceph OSDs using ceph-volume

The create subcommand calls the prepare subcommand, and then calls the activate subcommand.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the Ceph OSD nodes.
Note

If you prefer to have more control over the creation process, you can use the prepare and activate subcommands separately to create the OSD, instead of using create. You can use the two subcommands to gradually introduce new OSDs into a storage cluster, while avoiding having to rebalance large amounts of data. Both approaches work the same way, except that using the create subcommand causes the OSD to become up and in immediately after completion.

Procedure

  1. To create a new OSD:

    Syntax

    ceph-volume lvm create --bluestore --data VOLUME_GROUP/LOGICAL_VOLUME

    Example

    [root@osd ~]# ceph-volume lvm create --bluestore --data example_vg/data_lv

Additional Resources

7.8. Migrating BlueFS data

You can migrate the BlueStore file system (BlueFS) data, that is the RocksDB data, from the source volume to the target volume using the migrate LVM subcommand. The source volume, except the main one, is removed on success.

LVM volumes are primarily for the target only.

The new volumes are attached to the OSD, replacing one of the source drives.

Following are the placement rules for the LVM volumes:

  • If source list has DB or WAL volume, then the target device replaces it.
  • if source list has slow volume only, then explicit allocation using the new-db or new-wal command is needed.

The new-db and new-wal commands attaches the given logical volume to the given OSD as a DB or a WAL volume respectively.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the Ceph OSD node.
  • Ceph OSDs prepared by the ceph-volume utility.
  • Volume groups and Logical volumes are created.

Procedure

  1. Log in the cephadm shell:

    Example

    [root@host01 ~]# cephadm shell

  2. Stop the OSD to which you have to add the DB or the WAL device:

    Example

    [ceph: root@host01 /]# ceph orch daemon stop osd.1

  3. Mount the new devices to the container:

    Example

    [root@host01 ~]# cephadm shell --mount /var/lib/ceph/72436d46-ca06-11ec-9809-ac1f6b5635ee/osd.1:/var/lib/ceph/osd/ceph-1

  4. Attach the given logical volume to OSD as a DB/WAL device:

    Note

    This command fails if the OSD has an attached DB.

    Syntax

    ceph-volume lvm new-db --osd-id OSD_ID --osd-fsid OSD_FSID --target VOLUME_GROUP_NAME/LOGICAL_VOLUME_NAME

    Example

    [ceph: root@host01 /]# ceph-volume lvm new-db --osd-id 1 --osd-fsid 7ce687d9-07e7-4f8f-a34e-d1b0efb89921 --target vgname/new_db
[ceph: root@host01 /]# ceph-volume lvm new-wal --osd-id 1 --osd-fsid 7ce687d9-07e7-4f8f-a34e-d1b0efb89921 --target vgname/new_wal

  5. You can migrate BlueFS data in the following ways:

    • Move BlueFS data from main device to LV that is already attached as DB:

      Syntax

      ceph-volume lvm migrate --osd-id OSD_ID --osd-fsid OSD_UUID --from data --target VOLUME_GROUP_NAME/LOGICAL_VOLUME_NAME

      Example

      [ceph: root@host01 /]# ceph-volume lvm migrate --osd-id 1 --osd-fsid 0263644D-0BF1-4D6D-BC34-28BD98AE3BC8 --from data --target vgname/db

    • Move BlueFS data from shared main device to LV which shall be attached as a new DB:

      Syntax

      ceph-volume lvm migrate --osd-id OSD_ID --osd-fsid OSD_UUID --from data --target VOLUME_GROUP_NAME/LOGICAL_VOLUME_NAME

      Example

      [ceph: root@host01 /]# ceph-volume lvm migrate --osd-id 1 --osd-fsid 0263644D-0BF1-4D6D-BC34-28BD98AE3BC8 --from data --target vgname/new_db

    • Move BlueFS data from DB device to new LV, and replace the DB device:

      Syntax

      ceph-volume lvm migrate --osd-id OSD_ID --osd-fsid OSD_UUID --from db --target VOLUME_GROUP_NAME/LOGICAL_VOLUME_NAME

      Example

      [ceph: root@host01 /]# ceph-volume lvm migrate --osd-id 1 --osd-fsid 0263644D-0BF1-4D6D-BC34-28BD98AE3BC8 --from db --target vgname/new_db

    • Move BlueFS data from main and DB devices to new LV, and replace the DB device:

      Syntax

      ceph-volume lvm migrate --osd-id OSD_ID --osd-fsid OSD_UUID --from data db --target VOLUME_GROUP_NAME/LOGICAL_VOLUME_NAME

      Example

      [ceph: root@host01 /]# ceph-volume lvm migrate --osd-id 1 --osd-fsid 0263644D-0BF1-4D6D-BC34-28BD98AE3BC8 --from data db --target vgname/new_db

    • Move BlueFS data from main, DB, and WAL devices to new LV, remove the WAL device, and replace the the DB device:

      Syntax

      ceph-volume lvm migrate --osd-id OSD_ID --osd-fsid OSD_UUID --from data db wal --target VOLUME_GROUP_NAME/LOGICAL_VOLUME_NAME

      Example

      [ceph: root@host01 /]# ceph-volume lvm migrate --osd-id 1 --osd-fsid 0263644D-0BF1-4D6D-BC34-28BD98AE3BC8 --from data db --target vgname/new_db

    • Move BlueFS data from main, DB, and WAL devices to the main device, remove the WAL and DB devices:

      Syntax

      ceph-volume lvm migrate --osd-id OSD_ID --osd-fsid OSD_UUID --from db wal --target VOLUME_GROUP_NAME/LOGICAL_VOLUME_NAME

      Example

      [ceph: root@host01 /]# ceph-volume lvm migrate --osd-id 1 --osd-fsid 0263644D-0BF1-4D6D-BC34-28BD98AE3BC8 --from db wal --target vgname/data

7.9. Expanding BlueFS DB device

You can expand the storage of the BlueStore File System (BlueFS) data that is the RocksDB data of ceph-volume created OSDs with the ceph-bluestore tool.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Ceph OSDs are prepared by the ceph-volume utility.
  • Volume groups and Logical volumes are created.
Note

Run these steps on the host where the OSD is deployed.

Procedure

  1. Optional: Inside the cephadm shell, list the devices in the Red Hat Ceph Storage cluster.

    Example

    [ceph: root@host01 /]# ceph-volume lvm list

====== osd.3 =======

  [db]          /dev/db-test/db1

      block device              /dev/test/lv1
      block uuid                N5zoix-FePe-uExe-UngY-D9YG-BMs0-1tTDyB
      cephx lockbox secret
      cluster fsid              1a6112da-ed05-11ee-bacd-525400565cda
      cluster name              ceph
      crush device class
      db device                 /dev/db-test/db1
      db uuid                   1TUaDY-3mEt-fReP-cyB2-JyZ1-oUPa-hKPfo6
      encrypted                 0
      osd fsid                  94ff742c-7bfd-4fb5-8dc4-843d10ac6731
      osd id                    3
      osdspec affinity          None
      type                      db
      vdo                       0
      devices                   /dev/vdh

  [block]       /dev/test/lv1

      block device              /dev/test/lv1
      block uuid                N5zoix-FePe-uExe-UngY-D9YG-BMs0-1tTDyB
      cephx lockbox secret
      cluster fsid              1a6112da-ed05-11ee-bacd-525400565cda
      cluster name              ceph
      crush device class
      db device                 /dev/db-test/db1
      db uuid                   1TUaDY-3mEt-fReP-cyB2-JyZ1-oUPa-hKPfo6
      encrypted                 0
      osd fsid                  94ff742c-7bfd-4fb5-8dc4-843d10ac6731
      osd id                    3
      osdspec affinity          None
      type                      block
      vdo                       0
      devices                   /dev/vdg

  2. Get the volume group information:

    Example

    [root@host01 ~]# vgs

VG                                        #PV #LV #SN Attr   VSize    VFree
db-test                                     1   1   0 wz--n- <200.00g <160.00g
test                                        1   1   0 wz--n- <200.00g <170.00g

  3. Stop the Ceph OSD service:

    Example

    [root@host01 ~]# systemctl stop host01a6112da-ed05-11ee-bacd-525400565cda@osd.3.service

  4. Resize, shrink, and expand the logical volumes:

    Example

    [root@host01 ~]# lvresize -l 100%FREE /dev/db-test/db1
Size of logical volume db-test/db1 changed from 40.00 GiB (10240 extents) to <160.00 GiB (40959 extents).
Logical volume db-test/db1 successfully resized.

  5. Launch the cephadm shell:

    Syntax

    cephadm shell -m /var/lib/ceph/CLUSTER_FSID/osd.OSD_ID:/var/lib/ceph/osd/ceph-OSD_ID:z

    Example

    [root@host01 ~]# cephadm shell -m /var/lib/ceph/1a6112da-ed05-11ee-bacd-525400565cda/osd.3:/var/lib/ceph/osd/ceph-3:z

    The ceph-bluestore-tool needs to access the BlueStore data from within the cephadm shell container, so it must be bind-mounted. Use the -m option to make the BlueStore data available.

  6. Check the size of the Rocks DB before expansion:

    Syntax

    ceph-bluestore-tool show-label --path OSD_DIRECTORY_PATH

    Example

    [ceph: root@host01 /]# ceph-bluestore-tool show-label --path /var/lib/ceph/osd/ceph-3/
inferring bluefs devices from bluestore path
{
    "/var/lib/ceph/osd/ceph-3/block": {
        "osd_uuid": "94ff742c-7bfd-4fb5-8dc4-843d10ac6731",
        "size": 32212254720,
        "btime": "2024-04-03T08:34:12.742848+0000",
        "description": "main",
        "bfm_blocks": "7864320",
        "bfm_blocks_per_key": "128",
        "bfm_bytes_per_block": "4096",
        "bfm_size": "32212254720",
        "bluefs": "1",
        "ceph_fsid": "1a6112da-ed05-11ee-bacd-525400565cda",
        "ceph_version_when_created": "ceph version 19.0.0-2493-gd82c9aa1 (d82c9aa17f09785fe698d262f9601d87bb79f962) squid (dev)",
        "created_at": "2024-04-03T08:34:15.637253Z",
        "elastic_shared_blobs": "1",
        "kv_backend": "rocksdb",
        "magic": "ceph osd volume v026",
        "mkfs_done": "yes",
        "osd_key": "AQCEFA1m9xuwABAAwKEHkASVbgB1GVt5jYC2Sg==",
        "osdspec_affinity": "None",
        "ready": "ready",
        "require_osd_release": "19",
        "whoami": "3"
    },
    "/var/lib/ceph/osd/ceph-3/block.db": {
        "osd_uuid": "94ff742c-7bfd-4fb5-8dc4-843d10ac6731",
        "size": 40794497536,
        "btime": "2024-04-03T08:34:12.748816+0000",
        "description": "bluefs db"
    }
}

  7. Expand the BlueStore device:

    Syntax

    ceph-bluestore-tool bluefs-bdev-expand --path OSD_DIRECTORY_PATH

    Example

    [ceph: root@host01 /]# ceph-bluestore-tool bluefs-bdev-expand --path /var/lib/ceph/osd/ceph-3/
inferring bluefs devices from bluestore path
1 : device size 0x27ffbfe000 : using 0x2300000(35 MiB)
2 : device size 0x780000000 : using 0x52000(328 KiB)
Expanding DB/WAL...
1 : expanding  to 0x171794497536
1 : size label updated to 171794497536

  8. Verify the block.db is expanded:

    Syntax

    ceph-bluestore-tool show-label --path OSD_DIRECTORY_PATH

    Example

    [ceph: root@host01 /]# ceph-bluestore-tool show-label --path /var/lib/ceph/osd/ceph-3/
inferring bluefs devices from bluestore path
{
    "/var/lib/ceph/osd/ceph-3/block": {
        "osd_uuid": "94ff742c-7bfd-4fb5-8dc4-843d10ac6731",
        "size": 32212254720,
        "btime": "2024-04-03T08:34:12.742848+0000",
        "description": "main",
        "bfm_blocks": "7864320",
        "bfm_blocks_per_key": "128",
        "bfm_bytes_per_block": "4096",
        "bfm_size": "32212254720",
        "bluefs": "1",
        "ceph_fsid": "1a6112da-ed05-11ee-bacd-525400565cda",
        "ceph_version_when_created": "ceph version 19.0.0-2493-gd82c9aa1 (d82c9aa17f09785fe698d262f9601d87bb79f962) squid (dev)",
        "created_at": "2024-04-03T08:34:15.637253Z",
        "elastic_shared_blobs": "1",
        "kv_backend": "rocksdb",
        "magic": "ceph osd volume v026",
        "mkfs_done": "yes",
        "osd_key": "AQCEFA1m9xuwABAAwKEHkASVbgB1GVt5jYC2Sg==",
        "osdspec_affinity": "None",
        "ready": "ready",
        "require_osd_release": "19",
        "whoami": "3"
    },
    "/var/lib/ceph/osd/ceph-3/block.db": {
        "osd_uuid": "94ff742c-7bfd-4fb5-8dc4-843d10ac6731",
        "size": 171794497536,
        "btime": "2024-04-03T08:34:12.748816+0000",
        "description": "bluefs db"
    }
}

  9. Exit the shell and restart the OSD:

    Example

    [root@host01 ~]# systemctl start host01a6112da-ed05-11ee-bacd-525400565cda@osd.3.service
osd.3              host01               running (15s)     0s ago  13m    46.9M    4096M  19.0.0-2493-gd82c9aa1  3714003597ec  02150b3b6877

7.10. Using batch mode with ceph-volume

The batch subcommand automates the creation of multiple OSDs when single devices are provided.

The ceph-volume command decides the best method to use to create the OSDs, based on drive type. Ceph OSD optimization depends on the available devices:

  • If all devices are traditional hard drives, batch creates one OSD per device.
  • If all devices are solid state drives, batch creates two OSDs per device.
  • If there is a mix of traditional hard drives and solid state drives, batch uses the traditional hard drives for data, and creates the largest possible journal (block.db) on the solid state drive.
Note

The batch subcommand does not support the creation of a separate logical volume for the write-ahead-log (block.wal) device.

Prerequisites

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

Procedure

  1. To create OSDs on several drives:

    Syntax

    ceph-volume lvm batch --bluestore PATH_TO_DEVICE [PATH_TO_DEVICE]

    Example

    [ceph: root@host01 /]# ceph-volume lvm batch --bluestore /dev/sda /dev/sdb /dev/nvme0n1

Additional Resources

7.11. Zapping data using ceph-volume

The zap subcommand removes all data and filesystems from a logical volume or partition.

You can use the zap subcommand to zap logical volumes, partitions, or raw devices that are used by Ceph OSDs for reuse. Any filesystems present on the given logical volume or partition are removed and all data is purged.

Optionally, you can use the --destroy flag for complete removal of a logical volume, partition, or the physical device.

Prerequisites

  • A running Red Hat Ceph Storage cluster.
  • Root-level access to the Ceph OSD node.

Procedure

  • Zap the logical volume:

    Syntax

    ceph-volume lvm zap VOLUME_GROUP_NAME/LOGICAL_VOLUME_NAME [--destroy]

    Example

    [ceph: root@host01 /]# ceph-volume lvm zap osd-vg/data-lv

  • Zap the partition:

    Syntax

    ceph-volume lvm zap DEVICE_PATH_PARTITION [--destroy]

    Example

    [ceph: root@host01 /]# ceph-volume lvm zap /dev/sdc1

  • Zap the raw device:

    Syntax

    ceph-volume lvm zap DEVICE_PATH --destroy

    Example

    [ceph: root@host01 /]# ceph-volume lvm zap /dev/sdc --destroy

  • Purge multiple devices with the OSD ID:

    Syntax

    ceph-volume lvm zap --destroy --osd-id OSD_ID

    Example

    [ceph: root@host01 /]# ceph-volume lvm zap --destroy --osd-id 16

    Note

    All the relative devices are zapped.

  • Purge OSDs with the FSID:

    Syntax

    ceph-volume lvm zap --destroy --osd-fsid OSD_FSID

    Example

    [ceph: root@host01 /]# ceph-volume lvm zap --destroy --osd-fsid 65d7b6b1-e41a-4a3c-b363-83ade63cb32b

    Note

    All the relative devices are zapped.

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