FilesystemSubVolumeGroup CRD - Rook

!!! info This guide assumes you have created a Rook cluster as explained in the main Quickstart guide

Rook allows creation of Ceph Filesystem SubVolumeGroups through the custom resource definitions (CRDs). Filesystem subvolume groups are an abstraction for a directory level higher than Filesystem subvolumes to effect policies (e.g., File layouts) across a set of subvolumes. For more information about CephFS volume, subvolumegroup and subvolume refer to the Ceph docs.

Creating daemon

To get you started, here is a simple example of a CRD to create a subvolumegroup on the CephFilesystem "myfs".

yaml

apiVersion: ceph.rook.io/v1
kind: CephFilesystemSubVolumeGroup
metadata:
  name: group-a
  namespace: rook-ceph # namespace:cluster
spec:
  # The name of the subvolume group. If not set, the default is the name of the subvolumeGroup CR.
  name: csi
  # filesystemName is the metadata name of the CephFilesystem CR where the subvolume group will be created
  filesystemName: myfs
  # reference https://docs.ceph.com/en/latest/cephfs/fs-volumes/#pinning-subvolumes-and-subvolume-groups
  # only one out of (export, distributed, random) can be set at a time
  # by default pinning is set with value: distributed=1
  # for disabling default values set (distributed=0)
  pinning:
    distributed: 1 # distributed=<0, 1> (disabled=0)
    # export:      # export=<0-256> (disabled=-1)
    # random:      # random=[0.0, 1.0](disabled=0.0)
  # Quota size of the subvolume group.
  #quota: 10G
  # data pool name for the subvolume group layout instead of the default data pool.
  #dataPoolName: myfs-replicated

Settings

If any setting is unspecified, a suitable default will be used automatically.

CephFilesystemSubVolumeGroup metadata

name: The name that will be used for the Ceph Filesystem subvolume group.

CephFilesystemSubVolumeGroup spec

name: The spec name that will be used for the Ceph Filesystem subvolume group if not set metadata name will be used.
filesystemName: The metadata name of the CephFilesystem CR where the subvolume group will be created.
quota: Quota size of the Ceph Filesystem subvolume group.
dataPoolName: The data pool name for the subvolume group layout instead of the default data pool.
pinning: To distribute load across MDS ranks in predictable and stable ways. See the Ceph doc for Pinning subvolume groups.
- distributed: Range: <0, 1>, for disabling it set to 0
- export: Range: <0-256>, for disabling it set to -1
- random: Range: [0.0, 1.0], for disabling it set to 0.0

!!! note Only one out of (export, distributed, random) can be set at a time. By default pinning is set with value: distributed=1.

Create a storage class for the subvolume group

Create a CephFilesystem CR
Create a CephFilesystemSubvolumegroup CR

Note The clusterID can be explicitly set in the spec of the CephFilesystemSubVolumeGroup CR. If it is not set, Rook will auto-generate the clusterID.

Extract the clusterID from the status of the CephFilesystemSubvolumegroup CR:

bash

$ kubectl -n rook-ceph get cephfilesystemsubvolumegroup <name> -o jsonpath="{.status.info.clusterID}"
80fc4f4bacc064be641633e6ed25ba7e

This returns spec.clusterID if present, otherwise falls back to the auto generated one.

Set the clusterID in the StorageClass, VolumeSnapshotClass, and VolumeGroupSnapshotClass to this value instead of the name of the cluster namespace