HP XP Continuous Access Software - Manual (Page 170)

170 HP StorageWorks Disk Array XP RAID Manager: User’s Guide
–swap [s|p] (CA only) The –swaps option is executed from the
S-VOL when there is no host on the P-VOL side to
help. A remote host must be connected to the S-VOL.
Typically executed in PSUS (SSWS) state (after a
horctakeover
) to facilitate fast failback without
requiring a full copy.
Unlike –swaps, –swapp requires the cooperation of
hosts at both sides. It is the equivalent of –swaps,
executed from the original P-VOL side.
For both –swaps and –swapp, the delta data from the
original S-VOL becomes dominant and is copied to the
original P-VOL, then the P-VOL/S-VOL designations
are swapped.
The application can continue to run at the remote
failover site during this operation. At completion, the
remote failover site will own the P-VOL. When
desired, a very fast horctakeover will allow a fast
failback of the application from the recovery site to the
original site.
The following figure describes the –swap[s|p]
operation. The left side of the diagram shows T0 (time
zero) for both the P-VOL and S-VOL, before command
execution. The right side shows T1, after command
execution.
P-VOL S-VOL
Altered Data
R or R/W R/W
NEW_SVOL NEW_PVOL
R/W
R
pairresync -swaps on SVOL
or
pairresync -swapp on PVOL
T0
T1 T0
→ T1 situation T1
T0