Dell EMC Solutions Enabler 9.2 SRDF Family CLI User Guide

An incremental restore re-synchronizes data from the target (R2) to the source (R1) device when a split RDF pair is rejoined. Only those tracks on the target (R2) device that changed while the SRDF pair was split are copied, greatly reducing the amount of data that is copied.

During an incremental restore SRDF carries out the following activities for each specified SRDF pair in a device group:

1. Set the source (R1) device to write disabled to its local hosts.
2. Set the target (R2) device to write disabled to its local hosts.
3. Suspend traffic on the SRDF links.
4. Refresh the invalid tracks on the source (R1) device from the changed tracks on the target (R2) side. The track tables are merged between the R1 and R2 side.
5. Resume traffic on the SRDF links.
6. Set the source (R1) device to read/write enabled to its local hosts.

In SRDF/S configurations, when the restore control operation has successfully completed and the device pair is in the Synchronized state, the source (R1) device and the target (R2) device contain identical data.

In SRDF/A configurations, when the restore control operation has successfully completed and the device pair is in the Consistent state, the target (R2) device contains dependent write consistent data.

In SRDF/Metro configurations, once the source (R1) device and the target (R2) device contain identical data, the pair state is changed to either ActiveActive or ActiveBias and the R2 side is made RW-accessible to the host(s).

R2 may be set to read/write disabled (not ready) set the value of SYMAPI_RDF_RW_DISABLE_R2 to ENABLE in the options file. For more information, refer to the Dell Solutions Enabler CLI Reference Guide

The following image shows the incremental restore of an SRDF pair.

Syntax

Use incremental restore for a device group, composite group, storage group, or device file:

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

Include the -use_bias option in SRDF/Metro configurations to indicate that neither the Witness nor vWitness methods of determining bias are used:

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

For SRDF/A configurations, the restore operation must include all devices in the group unless the devices are exempt.

Use the verify command to confirm that the SRDF pairs are in the correct state:

Examples

To initiate an incremental restore on all SRDF pairs in the prod device group:

symrdf -g prod restore

To initiate an incremental restore on a list devices in a SRDF/Metro group where bias determines which side of the device pair remains accessible to the host:

symrdf -f /tmp/device_file -sid 085 -rdfg 86 restore -use_bias