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# Failover

Symmetrix Remote Data Facility (SRDF) facilitates the data replication from one storage system to another through a storage area network or Internet Protocol (IP) network.

## Prerequisites

See Roles and associated permissions to determine the user roles that can perform this task.

If the target (R2) volume is on a storage system running HYPERMAX OS or PowerMaxOS , and the mode of the source (R1) volume is Adaptive Copy Write Pending, SRDF sets the mode to Adaptive Copy Disk.

As a result of a failover (with establish or restore) operation, a cascaded R1 -> R21 -> R2 configuration can be created if any of the storage systems in the cascaded configuration is running HYPERMAX OS Q1 2015 SR or later.

This operation is blocked on SRDF groups that Global Mirror uses.

## About this task

In a period of scheduled downtime for maintenance, or after a serious system problem which has rendered either the host or storage system containing the source (R1) volumes unreachable, no read/write operations can occur on the source (R1) volumes. In this situation, the failover operation should be initiated to make the target (R2) volumes read/write enabled to their local hosts.

The Failing Over operation is not allowed on the non-Metro SRDF mirror when it results in a SRDF/Metro device becoming write-disabled (WD).

This operation can be invoked from multiple locations in the Unisphere user interface (Device group > SRDF Group, Device Group > SRDF Pairs, SG All Details > SRDF tab, PROTECTION dashboard) . Depending on where the operation is invoked, some of the steps below may not apply.

This operation can be invoked from multiple locations in the Unisphere user interface (Device group > SRDF Group, Device Group > SRDF Pairs, SG All Details > SRDF tab, PROTECTION dashboard) . Depending on where the operation is invoked, some of the steps below may not apply.

To initiate a failover:

## Steps

1. Select the storage system.
2. Click Protection to view the Protection dashboard and select SRDF from the Protected Storage Groups section of the summary panel.
3. Do the following, depending on whether you want to perform the operation at the group level or pair level:
   - Group level:
     1. Select a group, click , and select Failover . For storage groups with Celerra FBA emulation, a warning dialog is displayed indicating that the storage group may be managed externally using eNAS. To continue, click OK, otherwise click Cancel.
     2. Select the Use 2nd Hop option if including the second hop of a cascaded SRDF configuration (only applicable for device groups).
     3. Select the failover.
   - Pair level:
     1. Select a group, click , and click the number next to SRDF Pairs.
     2. Select one or more pairs, click , and select Failover .
     3. Select the failover.
4. Click Advanced Options to set the advanced options. Select the advanced options and click OK.
5. Do one of the following:
   - Click Run Now to perform the operation now.
   - Expand Run Now and click Add to Job List to add this task to the job list, from which you can schedule or run the task at your convenience. For more information, see Schedule jobs and Preview jobs.