HP XP Racks - Manual (Page 38)

Reverse resynchronization
After a failover, when the S-VOL is receiving updates from the host instead of the P-VOL, you can
resynchronize the P-VOL with the S-VOL by running the RAID Manager pairresync-swaps
command. Copy direction is from S-VOL-to-P-VOL.
The P-VOL and S-VOL are swapped in this operation: the secondary storage system S-VOL becomes
the P-VOL; the primary storage system P-VOL becomes the S-VOL.
The pairresync -swaps command is the only supported method for reverse resynchronizing
ESAM pairs.
Prerequisites
•
Make sure that:
All errors are cleared. ◦
◦ Pair status is SSWS.
•
Important: If a pair is shared by multiple hosts with VMware, access to the pair must be
managed uniformly. Otherwise, the pair can become inaccesible to one of the hosts. Before
performing this procedure, see
“Recovery for pairs shared by multiple hosts with VMware”
(page 66) .
Procedure
1. Run the RAID Manager pairresync -swaps command on the S-VOL.
The data in the RCU S-VOL is copied to the MCU P-VOL. Also, the P-VOL and S-VOL is
swapped. The MCU P-VOL becomes the S-VOL, and the RCU S-VOL becomes the P-VOL.
2. When the operation completes, verify that the pair is in PAIR status.
The following figure shows the swapping of an ESAM P-VOL and S-VOL.
Releasing a pair
You can release a pair when you no longer need to keep the P-VOL and S-VOL synchronized. You
can release a single pair or multiple pairs using the same procedure.
When you release a pair from the P-VOL, the primary storage system stops copy operations and
changes pair status of both P-VOL and S-VOL to SMPL. The system continues to accept write I/O
to the P-VOL volume, but does not keep track of the updates as differential data.
When you release a pair from the S-VOL, the secondary storage system changes S-VOL status to
SMPL, but does not change P-VOL status. When the primary storage system performs the next pair
38 Working with volume pairs