Backup & Restore Block PVC Technical preview

In IBM Storage Fusion 2.8 release, support is included for block volume mode PVs as a technical preview. Before 2.8, the Backup & Restore service only supported the backup of applications with filesystem volume mode PVs.

PV with volumeMode: Filesystem: The pod mounts it as a filesystem directory.

PV with volumeMode: Block: The pod mounts it as a raw block device without any filesystem on it. This mode provides the best performance as it eliminates the filesystem layer between the pod and the PV. A common application for block PVs is database and virtual machines, that is, Red Hat® OpenShift® Virtualization.

The detection and processing of Block volume mode PVs is automatic with no user configuration or changes to the input.

The CSI does not support the detection of changes in the Block volume mode PVs. As a result, every backup must read the entire Block volume mode PV to determine the incremental changes from the prior backups. The amount of time depends on the PV size. The resulting backup that is stored on S3 is still incremental and compressed.

Example Block volume mode PersistentVolume definition.

Note: The volumeMode designates the PersistentVolume as Filesystem or Block.


kind: PersistentVolume
apiVersion: v1
metadata:
  name: local-pv-76de1a29
  uid: 42643cc7-ac33-4536-b31b-6774524ee590
spec:
  capacity:
    storage: 3576Gi
  local:
    path: /mnt/local-storage/mylocalvs/nvme-Dell_Ent_NVMe_CM6_RI_3.84TB_Y2B0A01HTCE8
  accessModes:
    - ReadWriteOnce
  claimRef:
    kind: PersistentVolumeClaim
    namespace: openshift-storage
    name: ocs-deviceset-mylocalvs-0-data-4xh44d
    uid: 9abba1a3-6cd9-4d61-9f3e-95b29dab2094
    apiVersion: v1
    resourceVersion: '71161'
  persistentVolumeReclaimPolicy: Delete
  storageClassName: mylocalvs
  volumeMode: Block