mirror of
https://github.com/ceph/ceph-csi.git
synced 2024-11-23 23:00:19 +00:00
32a58f4e58
As shallow volumes are default for ROX pvc from snapshot, removing the details from doc for better clarity. Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>
63 lines
2.5 KiB
Markdown
63 lines
2.5 KiB
Markdown
# Provisioning and mounting CephFS snapshot-backed volumes
|
|
|
|
Snapshot-backed volumes allow CephFS subvolume snapshots to be exposed as
|
|
regular read-only PVCs. No data cloning is performed and provisioning such
|
|
volumes is done in constant time.
|
|
|
|
For more details please refer to [Snapshots as shallow read-only volumes](./design/proposals/cephfs-snapshot-shallow-ro-vol.md)
|
|
design document.
|
|
|
|
## Prerequisites
|
|
|
|
Prerequisites for this feature are the same as for creating PVCs with snapshot
|
|
volume source. See [Create snapshot and Clone Volume](./snap-clone.md) for more
|
|
information.
|
|
|
|
## Usage
|
|
|
|
### Provisioning a snapshot-backed volume from a volume snapshot
|
|
|
|
For provisioning new snapshot-backed volumes, following configuration must be
|
|
set for PVCs:
|
|
|
|
* PersistentVolumeClaim:
|
|
* Set `storageClassName` to point to your existing cephFS storage class.
|
|
* Define `spec.dataSource` for your desired source volume snapshot.
|
|
* Set `spec.accessModes` to `ReadOnlyMany`. This is the only access mode that
|
|
is supported by this feature.
|
|
|
|
Note:- We can also disable shallowVolume by setting `backingSnapshot: "false"
|
|
in cephFS storageclass. If the value is set in the storageclass when requested
|
|
for `ReadOnlyMany` PVC a clone will get created in ceph cluster.
|
|
|
|
### Mounting snapshots from pre-provisioned volumes
|
|
|
|
Steps for defining a PersistentVolume and PersistentVolumeClaim for
|
|
pre-provisioned CephFS subvolumes are identical to those described in
|
|
[Static PVC with ceph-csi](./static-pvc.md), except one additional parameter
|
|
must be specified: `backingSnapshotID`. CephFS-CSI driver will retrieve the
|
|
snapshot identified by the given ID from within the specified subvolume, and
|
|
expose it to workloads in read-only mode. Volume access mode must be set to
|
|
`ReadOnlyMany`.
|
|
|
|
Note that the snapshot retrieval is done by traversing `<rootPath>/.snap` and
|
|
searching for a directory that contains `backingSnapshotID` value in its name.
|
|
The specified snapshot ID does not necessarily need to be the complete directory
|
|
name inside `<rootPath>/.snap`, however it must be complete enough to uniquely
|
|
identify that directory.
|
|
|
|
Example:
|
|
|
|
```
|
|
$ ls .snap
|
|
_f279df14-6729-4342-b82f-166f45204233_1099511628283
|
|
_a364870e-6729-4342-b82f-166f45204233_1099635085072
|
|
```
|
|
|
|
`f279df14-6729-4342-b82f-166f45204233` would be considered a valid value for
|
|
`backingSnapshotID` volume parameter, whereas `6729-4342-b82f-166f45204233`
|
|
would not, as it would be ambiguous.
|
|
|
|
If the given snapshot ID is ambiguous, or no such snapshot is found, mounting
|
|
the PVC will fail with INVALID_ARGUMENT error code.
|