NetWorker 19.7 Snapshot Management Integration Guide

VMAX SRDF/S support

SRDF/S is a VMAX feature that maintains a synchronous, real-time copy of data at the LUN level between two VMAX storage arrays, one of which is local and the other remote.

To configure snapshots on a remote VMAX array with SRDF/S functionality, you must associate a source LUN (referred to as R1) on the local array with a source LUN (R2) on the remote array. The SRDF/S software maintains continuous synchronization of the two sources by copying all changes on one LUN device to the other.

For typical snapshot operations, the remote R2 LUN has its own mirror that NetWorker uses for snapshot creation and snapshot clones. A mirror is optional on the local R1 LUN. When NetWorker creates an SRDF/S snapshot, it validates the synchronization of the R1 and R2 devices and then syncs/splits the mirror of the R2 device. This split of the mirror creates the snapshot, which represents a third copy of the data. If the NetWorker policy specifies a clone, then NetWorker performs the clone from this mirror.

NetWorker also supports a direct R2 backup, with no snapshot. In this operation, NetWorker ensures the synchronization of the R1 and R2 devices, suspends the link between the R1 and R2 devices, and performs a clone directly from the R2 source LUN. After the clone completes, NetWorker reestablishes the link. The snapshot policy must have a Retain Snapshots value of 0 or the clone will fail.

SRDF/S requirements and support for snapshot operations are as follows:

• When using a direct R2 backup, R2 mirrors must be visible and available to the mount host.
• NetWorker automatically determines the state of the SRDF/S link at runtime. There is no requirement for manually configured environment variables or application variables.
• If there is no SRDF/S link at the beginning of an operation, then the backup or restore operation will fail.
• NetWorker does not support any changes to the SRDF/S link mode made during backup or restore operations.
• If the RDF link is in a failed over or failed back state, the snapshot operations will fail.
• Mirror replication cannot transition between asynchronous and synchronous modes during any NSM operation. The mode must remain constant.
• NetWorker does not support the creation of snapshots of file systems or of volume groups that cross SRDF/RA groups.
• NetWorker supports only single-hop remote connections.
• NetWorker supports only TF/Mirror (RBCV) in asynchronous copy (SRDF/A) environments and does not support concurrent RDF and STAR configurations and modes.

Rollbacks in the SRDF/S environment provides specific details on rollback operations in this environment.