HP Storage Mirroring V5 Software - Manual (Page 45)

HP StorageWorks Storage Mirroring Application Manager user’s guide 35
NOTE: Three scripts are automatically generated by the Application Manager during configuration. The
scripts are copied to the Storage Mirroring installation directory on the specified server using the administrative
share for that server’s drive.
Failover Script —A post-failover script (
post_failover_LN.txt
) is executed after the core failover processes
have completed on the target server. The primary function of the post-failover script is to start the resources on
the target.
Failback Script —A pre-failback script (
pre_failback_LN.txt
) is executed before failback processing occurs
on the target server. The primary function of this script is to stop resources on the target.
Restore Script —A post-restore script (
post_restore_LN.txt
) is not executed automatically, though it is
provided on the source to perform actions that are generally required after data has been restored from the
target to source after a failover/failback. The primary function of this script is to restart resources on the source
server.
After the four resources are online and the mirroring has completed, the source cluster is considered protected
and the Application Manager starts monitoring the source for complete source failure.
Dealing with a failure
Graceful failover
At the user's discretion, the Storage Mirroring Application Manager can perform a graceful, or “soft” failover.
A soft failover means the source cluster remains up and running while the EVS is transferred to the target
cluster. This can be accomplished by using the failover button in Storage Mirroring Application Manager. The
steps the Application Manager takes to transfer the EVS from the source cluster to the target are the same as
during a site failure failover, which is described in ” Site failure failover ” on page 35. The only difference is that
in a soft failover, the source cluster resources are taken offline gracefully.
Site failure failover
If the Storage Mirroring Application Manager detects that the source cluster has failed completely, it will
display a prompt asking if a failover is desired. The time it takes for the Application Manager to realize a
complete source cluster failure varies greatly. At times, the prompt can be seconds after the failure, or, it might
take several minutes. If you want the prompt to appear more quickly and you know that the source cluster has
failed, you can decrease the amount of wait time by closing the Application Manager, then re-opening it.
When a failover is initiated, the following steps occur:
1. The Storage Mirroring Application Manager waits on the target replication queue to empty.
2. The
exchfailover.exe
utility fails over the virtual protocols of the EVS.
3. The resources are created on the target cluster.
• The resources are created in the same order as they appeared on the source cluster.
• The resources are configured exactly as they were on the source cluster.
4. The resources are brought online.
5. The DNS failover utility is used to lock the source DNS record.
Differences in failback
The process used to failback to the source cluster is the same as any other cluster failover method. The only
difference is the EVS is now on both the source and target clusters.
To failback to the source cluster, bring the source cluster online, then use the Storage Mirroring Application
Manager to failback.