add docs for backup pvc config support

Signed-off-by: Shubham Pampattiwar <[email protected]>

site/content/docs/main/data-movement-backup-pvc-configuration.md

@@ -0,0 +1,46 @@
+---
+title: "BackupPVC Configuration for Data Movement Backup"
+layout: docs
+---
+
+`BackupPVC` is an intermediate PVC created by the exposer for VGDP (Velero Generic Data Path) to access data from during
+the data movement backup operation.
+
+In some scenarios users may need to configure some advanced options of the backupPVC so that the data movement backup
+operation could perform better.
+
+Velero introduces a new section in `node-agent-config` configMap called `backupPVC`, through which you can specify the following
+configurations:
+
+- `storageClass`: This specifies the storage class to be used for the backupPVC. If this value does not exist or is empty then by 
+default the source PVC's storage class will be used.
+
+- `readOnly`: This is a boolean value. If set to `true` then `ReadOnlyMany` will be the only value set to the backupPVC's access modes. Otherwise 
+`ReadWriteOnce` value will be used.
+
+A sample of `backupPVC` config as part of the `node-agent-config` configMap would look like:
+```json
+{
+    "backupPVC": {
+        "storage-class-1": {
+            "storageClass": "backupPVC-storage-class",
+            "readOnly": true
+        },
+        "storage-class-2": {
+            "storageClass": "backupPVC-storage-class"
+        },
+        "storage-class-3": {
+            "readOnly": true
+        }        
+    }
+}
+```
+
+**Note:** 
+- Users should make sure that the storage class specified in `backupPVC` config should exist in the cluster and can be used by the
+`backupPVC`, otherwise the corresponding DataUpload CR will stay in `Accepted` phase until timeout (data movement prepare timeout value is 30m by default).
+- If the users are setting `readOnly` value as `true` in the `backupPVC` config then they must also make sure that the storage class that is being used for 
+`backupPVC` should support creation of `ReadOnlyMany` PVC from a snapshot,  otherwise the corresponding DataUpload CR will stay in `Accepted` phase until
+timeout (data movement prepare timeout value is 30m by default).
+- If any of the above problems occur, then the DataUpload CR is `canceled` after timeout, and the backupPod and backupPVC will be deleted, and the backup
+will be marked as `PartiallyFailed`.

site/data/docs/main-toc.yml

@@ -52,7 +52,9 @@ toc:
       - page: CSI Snapshot Data Movement
         url: /csi-snapshot-data-movement
       - page: Node-agent Concurrency
-        url: /node-agent-concurrency        
+        url: /node-agent-concurrency
+      - page: Backup PVC Configuration
+        url: /data-movement-backup-pvc-configuration
       - page: Verifying Self-signed Certificates
         url: /self-signed-certificates
       - page: Changing RBAC permissions