Dell EMC Solutions Enabler 9.2 SRDF Family CLI User Guide

Failovers are used to move processing to the R2 devices during scheduled maintenance (planned failover) or when an outage makes the R1 devices unreachable (unplanned failover).

A failover transfers processing to the target (R2) devices and makes them read/write enabled to their local hosts.

Failover initiates the following activities for each specified SRDF pair in a device group:

• If the source (R1) device is operational, the SRDF links are suspended.
• If the source side is operational, the source (R1) device is write disabled to its local hosts.
• The target (R2) device is read/write enabled to its local hosts.

A planned failover is a controlled failover operation to test the robustness of the disaster restart solution, or to perform maintenance at the primary site. The secondary site temporarily becomes the primary/production site.

A planned failover includes the following general steps:

1. Shut down all applications on the production host.
2. Take all SRDF links between array A and array B offline to suspend remote mirroring.
3. When SRDF/CG is enabled, disable consistency groups between array A and array B.
4. Swap personalities between R1 and R2 devices.

   SRDF devices at array B are now R1 devices.

   SRDF devices at array A are now R2 devices.

   In SRDF/S configurations, devices are ready to resume production operations at array B.

5. When SRDF/CG is used, enable consistency between array B and array A.
6. Bring all SRDF links between array B and array A online to resume remote mirroring.
7. Start production applications from the host attached to array B.

An unplanned failover moves production applications from the primary site to the secondary site after an unanticipated outage at the primary site, and the primary site is not available.

An unplanned failover includes the following general steps:

1. Take all SRDF links between array A and array B offline to suspend remote mirroring.
2. Change the R2 device states to Read/Write to the secondary host connected to array B.
3. Start applications on the secondary host and resume production to write-enabled R2 devices in array B.

The following image shows failover of an SRDF pair.

Syntax

Use failover for a device group, composite group, storage group, or device file:

symrdf -g DgName failover
symrdf -cg CgName failover
symrdf -sg SgName failover
symrdf -f[ile] FileName failover

Examples

To perform a failover on all the pairs in the prod device group:

symrdf -g prod failover