There are problems with the latest version of PowerHA 7.1 software with the latest fixes (SP3) from December 2010. This is the first version of the popular IBM clustering software for AIX which takes advantage of CAA (Cluster Aware AIX). CAA is available on the AIX 6.1 TL6 and AIX 7.1 TL0 base media. After installing a new cluster and attempting a start of the cluster the first node came up fine but the second one did not.  A simple reboot was necessary to get the second node to start. Once both nodes were up and running the halt command was used to failover the resource group to the second node.  It took about 1.5 minutes for the failover to work.  This is longer than expected since this new version is supposed to detect node failure faster. Once the first node came back up it didn't join the cluster and then the second node crashed!  After restarting the second node it didn't join the cluster either. At this point PowerHA 7.1 was removed and PowerHA 6.1 (with SP5) was installed.  This version worked flawlessly. We are looking forward to re-testing these scenarios when PowerHA 7.1 SP4 is available.

** October 28, 2011 - Update**

"I have been able to work with PowerHA 7.1 SP4 and AIX 6.1 TL6 SP5.  This combination is now working great.  The previous problems have now been fixed. 

CAA has been updated with the newer Service Pack for AIX.  This was the key to the stability of the PowerHA 7.1 cluster"

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