HP XP Racks - Manual (Page 66)

The following table lists whether failover or failback will occur based on the order in which you
restore the paths (owner path first or non-owner path first).
Will failover or failback occur? Order for restoring paths Volume receiving host I/O
No. 1. Owner path Primary system P-VOL
2. Non-owner path
Yes, if data in the S-VOL is newer than in the
P-VOL, failover occurs after the non-owner path is 1. Non-Owner path
2. Owner path
restored. However, failover does not occur if data
in the S-VOL is older. Check this by viewing the
VOL Access column on the Pair Operation window
for the P-VOL. If you see Access (Lock), then the
P-VOL is receiving host I/O.
Yes, failover occurs after the owner path is
restored. However, if data in the primary storage 1. Owner path
2. Non-owner path
Secondary system P-VOL
(original S-VOL)
system S-VOL is older, failover does not occur.
Check the VOL Access column on the Pair
Operation window for the secondary storage
system P-VOL. If you see Access (Lock), then this
volume is receiving host I/O.
No. 1. Non-Owner path
2. Owner path
Allowing host I/O to an out-of-date S-VOL
If you attempt a recovery of a primary storage system, you might need to use the S-VOL to continue
host operations, even though its data is older than the data on the P-VOL.
Contact the HP Support Center and ask to have the appropriate system option turned ON. This
enables the S-VOL to receive host I/O.
NOTE: The system option applies to the whole storage system. You cannot set this option to an
individual pair or pairs.
To continue using the pair after the failure has been cleared, release and re-create the pair. The
storage system builds the initial copy from the P-VOL to the S-VOL.
Recovery for pairs shared by multiple hosts with VMware
When a pair is shared by multiple hosts with VMware, it is important that access to the pair is
managed uniformly. Otherwise, the pair can become inaccessible to one of the hosts.
The following procedures are necessary for recovery using the horctakeover and pairresync swaps
commands, and for failover. For more information regarding changing host access or status, see
the Dynamic Link Manager User Guide for your operating system.
Managing access for hortcakeover and pairresync swaps commands
1. Switch access from all hosts to the pair via owner paths to access via non-owner paths.
2. When all host access is via non-owner paths, execute the horctakeover or pairresync
–swaps
command on the S-VOL.
Changing owner path status for failover
Procedure 1 When using Hitachi Dynamic Link Manager a version earlier than v. 7.6.0
1. Specify a host to access the pair, and move all guest OSs to the specified host.
2. Shut down all hosts other than the specified host in the Step 1.
3. Make online the owner paths of the hosts that access the pair.
66 Disaster recovery