How Backup & Restore service backups up application data

Backup & Restore service includes support for block volume mode PVs along with the backup of applications with filesystem volume mode PVs. It also supports incremental backups for stateful data (PVC) using Fusion Backup & Restore.

You can backup an application data, and it consists of PVC data and resources. For the PVC data, you can use online backups or snapshots. You mount the snapshot as a separate PVC for independent processing of the backup without impacting the application. The first back is a full backup and all subsequent backups are incremental. The backups are store in a S3 repository or locally on the system using snapshots (not recommended). The detection and processing of Block volume mode PVs is automatic with no user configuration or changes to the input.

Backup and restore of PV

The Backup & Restore service can backup data hosted on both volumeMode: Block and Filesystem persistent volumes (PV). The detection and processing of the volumeMode is automatic and does not need any user configuration or changes.

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.

Example Block volume mode PersistentVolume definition.


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

Backup and restore of PVC data

Stateful data (PVC) backups with Fusion Backup & Restore are incremental, meaning that only new or changed data since the previous backup is sent to the backup storage location. After the initial backup, which copies all stateful data on the PVCs, subsequent backups only transfer new or modified data. After the first backup, the entire data is never copied again; instead, backups continue to send only new or changed data.

RADOS Block Device (RBD) storage class based volumes

In RBD storage class based volumes, change block detection capability speeds up processing time of the backup.

Resources

Kubernetes resource data is always copied in its entirety on each backup operation. Comparatively, the Kubernetes resource data represents a very small percentage of the total amount of data that gets transferred for the backup operation.