With HACMP clusters documentation is probably the most important issue. You cannot properly manage an HACMP cluster if you do not document it. Document the precise configuration of the complete cluster and document any changes you've carried out. Also document all management procedures and stick to them! The cluster snapshot facility is an excellent way of documenting your cluster.

Next step: get educated. You have to know exactly what you're doing on an HACMP cluster. If you have to manage a production cluster, getting a certification is a necessity. Don't ever let non-HACMP-educated UNIX administrators on your HACMP cluster nodes. They don't have a clue of what's going on and probably destroy your carefully layed-out configuration.

Geographically separated nodes are important! Too many cluster nodes just sit on top of each other in the same rack. What if there's a fire? Or a power outage? Having an HACMP cluster won't help you if both nodes are on a single location, use the same power, or the same network switches.

Put your HACMP logs in a sensible location. Don't put them in /tmp knowing that /tmp gets purged every night....

Test, test, test and test your cluster over again. Doing take-over tests every half year is best practice. Document your tests, and your test results.

Don't assume that your cluster is high available after installing the cluster software. There are a lot of other things to consider in your infrastructure to avoid single points of failures, like: No two nodes sharing the same I/O drawer; Power redundancy; No two storage or network adapters on the same SCSI backplane or bus; Redundancy in SAN HBA's; Application monitoring in place.



If you found this useful, here's more on the same topic(s) in our blog:

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• Error in HACMP in LVM
• PowerHA UI
• Email messages from the cron daemon
• VGDA out of sync