HP 3PAR Operating System Software - Manual (Page 141)

The transparent switchover is complete (see Figure 51 (page 141) ):
•
The system is now fully reversed and ready for another switchover request.
•
The switchover has occurred in such a way as to:
Manage host traffic without letting it time out.
◦
◦ Ensure that volume migration happens transparently to the applications on the host.
The target time to ensure that the host traffic does not time out is 60 seconds. This does not include
the subsequent recovery and reversal operations.
Figure 51 Manual Transparent Switchover Is Complete
Automatic Transparent Failover
The purpose of an automatic transparent failover is to migrate the service of host I/O from the
failed primary to the surviving secondary storage system. In an automatic transparent failover,
there can be no coordination of operation between the storage systems. Only those actions
performed on the secondary system, as described in
“Manual Transparent Switchover” (page 137) ,
are executed. The operation initiation sequence also differs somewhat from a manual transparent
switchover:
•
In a manual transparent switchover, the operation is initiated by issuing the setrcopy
switchover
command, on a remote-copy volume group basis, on the primary storage system.
•
In an automatic transparent failover, the trigger is provided to the surviving secondary storage
system by the Quorum Witness infrastructure and related software, which begin state transition
and activation of the secondary host paths for all applicable secondary volume groups.
The outcome of both the manual and the automatic peer-persistence operations will be the same,
in that the original secondary system will begin to service host I/O to the failed-over volume groups;
but in an automatic failover, replication will have stopped, and will remain unavailable until the
failed system is recovered.
HP 3PAR Peer Persistence Quorum
HP 3PAR Peer Persistence Phase 2, available with HP 3PAR OS 3.1.2 MU2, supports HP 3PAR
Quorum Witness. The quorum witness database acts as a repository for pairs of storage systems
HP 3PAR Peer Persistence Quorum 141