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This commit is the restructure the doc folder to include sub-folders like csi-addons, rbd, cephfs to contain related docs and other general docs can be placed under doc folder. This will enhance the doc structure will make it easier for the users to search the docs as it get more populated. Signed-off-by: yati1998 <ypadia@redhat.com>
63 lines
2.5 KiB
Markdown
63 lines
2.5 KiB
Markdown
# Provisioning and mounting CephFS snapshot-backed volumes
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Snapshot-backed volumes allow CephFS subvolume snapshots to be exposed as
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regular read-only PVCs. No data cloning is performed and provisioning such
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volumes is done in constant time.
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For more details please refer to [Snapshots as shallow read-only volumes](./design/proposals/cephfs-snapshot-shallow-ro-vol.md)
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design document.
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## Prerequisites
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Prerequisites for this feature are the same as for creating PVCs with snapshot
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volume source. See [Create snapshot and Clone Volume](./snap-clone.md) for more
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information.
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## Usage
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### Provisioning a snapshot-backed volume from a volume snapshot
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For provisioning new snapshot-backed volumes, following configuration must be
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set for PVCs:
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* PersistentVolumeClaim:
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* Set `storageClassName` to point to your existing cephFS storage class.
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* Define `spec.dataSource` for your desired source volume snapshot.
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* Set `spec.accessModes` to `ReadOnlyMany`. This is the only access mode that
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is supported by this feature.
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Note:- We can also disable shallowVolume by setting `backingSnapshot: "false"
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in cephFS storageclass. If the value is set in the storageclass when requested
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for `ReadOnlyMany` PVC a clone will get created in ceph cluster.
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### Mounting snapshots from pre-provisioned volumes
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Steps for defining a PersistentVolume and PersistentVolumeClaim for
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pre-provisioned CephFS subvolumes are identical to those described in
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[Static PVC with ceph-csi](./static-pvc.md), except one additional parameter
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must be specified: `backingSnapshotID`. CephFS-CSI driver will retrieve the
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snapshot identified by the given ID from within the specified subvolume, and
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expose it to workloads in read-only mode. Volume access mode must be set to
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`ReadOnlyMany`.
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Note that the snapshot retrieval is done by traversing `<rootPath>/.snap` and
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searching for a directory that contains `backingSnapshotID` value in its name.
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The specified snapshot ID does not necessarily need to be the complete directory
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name inside `<rootPath>/.snap`, however it must be complete enough to uniquely
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identify that directory.
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Example:
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```
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$ ls .snap
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_f279df14-6729-4342-b82f-166f45204233_1099511628283
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_a364870e-6729-4342-b82f-166f45204233_1099635085072
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```
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`f279df14-6729-4342-b82f-166f45204233` would be considered a valid value for
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`backingSnapshotID` volume parameter, whereas `6729-4342-b82f-166f45204233`
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would not, as it would be ambiguous.
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If the given snapshot ID is ambiguous, or no such snapshot is found, mounting
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the PVC will fail with INVALID_ARGUMENT error code.
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