Building Disaster Recovery Serviceguard Solutions Using Metrocluster with Continuous Access for P9000 and XP A.11.00

Data Maintenance with the Failure of a Metrocluster with Continuous Access
for P9000 and XP Failover
The following section describes data maintenance in the event of a Swap Takeover in a Metrocluster
Continuous Access P9000 or XP environment.
Swap Takeover Failure (for Continuous Access Device Group Pair Between DC1 and
DC2)
When the pair state of a Continuous Access device group between DC1 and DC2 is SVOL-PAIR
in local site and PVOL-PAIR in remote site (assume the Continuous Access-Journal pair to DC3 is
in normal state - PVOL_PAIR/ SVOL_PAIR), the Three Data Center software performs a swap
takeover.
The swap takeover would fail if there is an internal (unseen) error (that is, cache or shared memory
failure) in the device group pair. In this case, if the AUTO_NONCURDATA is set to 0, the package
will not be started and the SVOL state is change to SVOL_PSUE (SSWS) by the takeover command.
The PVOL site either remains in PVOL_PAIR or is changed to PVOL_PSUE.
The SVOL is in SVOL_PSUE(SSWS) meaning that the SVOL is read/write enabled and the data is
usable but not as current as PVOL. In this case, user can either (1) use FORCEFLAG to startup the
package on SVOL site or (2) fix the problem and resume the data replication with the following
procedures:
For Multi-Hop Bi-Link Configuration:
1. Split the Continuous Access device group pair between DC1 and DC2 completely (pairsplit
-g dg12 -S).
2. Split the Continuous Access-Journal device group pair completely (pairsplit -g dg23
-S).
3. Re-create the Continuous Access pair between DC1 and DC2 from original PVOL as source.
(use paircreate command).
4. Re-create the Continuous Access-Journal pair between DC2 and DC3 from original PVOL as
source. (use paircreate command).
5. Startup package on its primary site
For Multi-Target Bi-Link Configuration:
1. Split the Continuous Access device group pair between DC1 and DC2 completely (pairsplit
-g dg12 -S).
2. Re-create the Continuous Access device group pair between DC1 and DC2 from original
PVOL as source. (use paircreate command)
3. Startup package on its primary site.
For Tri-Link Configuration:
1. Split all the three device group pairs completely using pairsplit -S command.
2. Re-create all the three device group pairs from original PVOL as source using paircreate
command.
Takeover Timeout (for third data center)
When a package is being failed over to the third data center (SVOL of the Continuous Access-Journal
device group), the Metrocluster toolkit script issues takeover command on the SVOL. If the journal
group pair is flushing the journal data from its PVOL to SVOL and takeover timeout occurs, the
following situations would happen:
152 Designing a Three Data Center Disaster Recovery Solution