Building Disaster Recovery Serviceguard Solutions Using Continentalclusters for Linux B.01.00.00

Ensure you periodically review the following files for messages, warnings, and recommended
actions. HP recommends to review these files after system, data center, and application failures.
• /var/adm/syslog/syslog.log
• /etc/cmcluster/<package-name>/<package-name>.log
• /etc/cmcluster/<bkpackage-name/<bkpackage-name>.log
Using 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, depending
on which site you are on, use the pairresync command in one of the following two ways:
• pairresync -swapp—from the primary site.
• pairresync -swaps—from the failover 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
the volumes, with the PVOL becoming the SVOL and SVOL becoming the PVOL. With the
personalities swapped, data written to the volume on the failover site (now PVOL) are copied to
the SVOL, which is now running on the primary site. During this time, the package continues running
on the failover site. After resynchronization is complete, you can halt the package on the failover
site, and restart it on the primary site. Metrocluster swaps the personalities between the PVOL and
the SVOL, returning PVOL status to the primary site.
Additional points
• This toolkit might increase package startup time by 5 minutes or more. Packages with many
disk devices will take longer to start up than those with fewer devices because of the time
required to get device status from the P9000 and XP disk array or to synchronize.
NOTE: Long delays in package startup time will occur in situations when recovering from
broken pair affinity.
• The value of RUN_SCRIPT_TIMEOUT in the package ASCII file must be set to NO_TIMEOUT
or to a large enough value to take into consideration the extra startup time required for getting
status information from the P9000 and XP disk array. (See the earlier paragraph for more
information on the extra startup time).
• Online cluster configuration changes might require a Raid Manager configuration file to be
changed. Whenever the configuration file is changed, the Raid Manager instance must be
stopped and restarted. The Raid Manager instance must be running before any
Continentalclusters package movement occurs.
• A file system must not reside on more than one P9000 and XP frames for either the PVOL or
the SVOL. An LVM Logical Volume (LV) must not reside on more than one P9000 and XP
frames for either the PVOL or the SVOL.
• The application is responsible for data integrity, and must use the O_SYNC flag when ordering
of I/Os is important. Most relational database products are examples of applications that
ensure data integrity by using the O_SYNC flag.
• Each host must be connected to only the P9000 and XP disk array that contains either the
PVOL or the SVOL. A given host must not be connected to both the PVOL and the SVOL of a
Continuous Access pair.
48 Administering Continentalclusters