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Chapter 9. Ceph File System snapshots
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 snapshots
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.
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.
Additional Resources
- See the Creating a snapshot for a Ceph File System section in the Red Hat Ceph Storage File System Guide for more details.
- See the Creating a snapshot schedule for a Ceph File System section in the Red Hat Ceph Storage File System Guide for more details.
9.2. Creating a snapshot for a Ceph File System
You can create an immutable, point-in-time view of a Ceph File System (CephFS) by creating a snapshot.
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
Log into the Cephadm shell:
Example
[root@mds ~]# cephadm shell
For existing Ceph File Systems, enable the snapshotting feature:
Syntax
ceph fs set FILE_SYSTEM_NAME allow_new_snaps trueExample
[ceph: root@mds ~]# ceph fs set cephfs01 allow_new_snaps true
Create a new snapshot subdirectory under the
.snapdirectory:Syntax
mkdir NEW_DIRECTORY_PATHExample
[ceph: root@mds ~]# mkdir /.snap/new-snaps
This example creates the
new-snapssubdirectory, and this informs the Ceph Metadata Server (MDS) to start making snapshots.To delete snapshots:
Syntax
rmdir NEW_DIRECTORY_PATHExample
[ceph: root@mds ~]# rmdir /.snap/new-snaps
ImportantAttempting to delete root-level snapshots, which might contain underlying snapshots, will fail.
Additional Resources
- See the Ceph File System snapshot schedules section in the Red Hat Ceph Storage File System Guide for more details.
- See the Ceph File System snapshots section in the Red Hat Ceph Storage File System Guide for more details.
- See the Deployment of the Ceph File System section in the Red Hat Ceph Storage File System Guide.
