Building Disaster Recovery Serviceguard Solutions Using Metrocluster with Continuous Access XP P9000 for Linux B.12.00.00

Figure 12 Q-Marker and Q-CNT
• U(%): Displays the usage rate of the journal data.
• D-SZ: Displays the capacity for the journal data on the journal group.
• Seq#: Displays the serial number of the XP12000.
• Num: Displays the number of LDEV (journal volumes) configured for the journal group.
• LDEV#: Displays the first LDEV number of journal volumes.
Resynchronizing the device groups
After certain failures, data is no longer remotely protected. In order to restore data protection after
repairing or recovering from the failure, you must manually run the command pairresync. This
command must successfully complete for data protection to be restored.
Following is a partial list of failures that require running pairresync to restore disaster-tolerant
data protection:
• Failure of all Continuous Access links without restart of the application
• Failure of all Continuous Access links with Fence Level “DATA” with restart of the application
on a primary host
• Failure of the entire secondary Data Center for a given application package
• Failure of the secondary XP or P9000 Series disk array for a given application package while
the application is running on a primary host
After the package fails over to the secondary site due to the following is a partial list of failures it
requires resynchronization from the secondary site to restore data protection. Full resynchronization
is automatically initiated for the following failures by moving the application package back to its
primary host after repairing the failure:
• Failure of the entire primary data center for a given application package.
• Failure of the primary XP or P9000 Series disk array for a given application package.
• Failure of all Continuous Access links with restart of the application on a secondary host.
Pairs must be manually recreated if both the primary and secondary XP or P9000 Series disk array
are in SMPL (simplex) state.
Using special options in the pairresync Command
The pairresync command can be used with special options; after a failover in which the recovery
site has started the application, and has processed transaction data on the disk at the recovery
site, but the disks on the primary site are intact. After the Continuous Access link is fixed, use the
pairresync command in one of the following two ways depending on which site you are running
the command:
• pairresync -swapp—from the primary site.
• pairresync -swaps—from the recovery site.
These options take advantage of the fact that the recovery site maintains a bit-map of the modified
data sectors on the recovery array. Either version of the command will swap the personalities of
Administering a Metrocluster using Continuous Access XP/P9000 replication 43