Designing Disaster Tolerant High Availability Clusters, 10th Edition, March 2003 (B7660-90013)

Building a Metropolitan Cluster Using MetroCluster/CA
Maintaining a Cluster that uses MetroCluster/CA
Chapter 3 113
Resynchronizing
After certain failures, data is no longer remotely protected. In order to
restore disaster tolerant data protection after repairing or recovering
from the failure, you must manually run the command pairresync.
This command must successfully complete for disaster-tolerant 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 CA links without restart of the application
• Failure of all CA 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 Series disk array for a given application
package while the application is running on a primary host
Following is a partial list of failures that require full resynchronization
to restore disaster-tolerant data protection. Full resynchronization is
automatically initiated for these 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 all of the primary hosts for a given application package
• Failure of the primary XP Series disk array for a given application
package
• Failure of all CA links with restart of the application on a
secondary host
Pairs must be manually recreated if both the primary and secondary XP
Series disk array are in SMPL (simplex) state. Make sure you
periodically review the files syslog.log and
/etc/cmcluster/pkgname/pkgname.log for messages, warnings and
recommended actions. You should particularly review these files after
system, data center and/or application failures.
Full resynchronization must be manually initiated after repairing the
following failures: