Hi,
I need to upgrade one of my clusters from HACMP 5.41 to HACMP 6.1.
Is there an easy + clean way to do it ? Any hurdles I have to anticipate? What should I read - anything I found so far seems to talk only about HACMP 5.x - and looks pretty straight forward.
Thanks and regards
zxmaus
As always the answer is likely to be "it depends" 
So just some thoughts in advance...
By going from 5.4 to 6.1 you upgrade the version. So there might be more to consider than if you would just upgrade the release. It is almost impossible to foresee what might happen at what stage. E.g. do you upgrade RSCT also and if yes, how does upgrading RSCT work out? So to really know what is going to happen this has to be tested in a testing environment. If you can test, a rolling migration might be your choice.
In case you cannot test the upgrade with clones I would not use any online migration method offered by IBM but recreate the cluster. This is not as much work as it sounds. You can use either snapshot or (if IBM did not change the XML files from 5.4 to 6.1 again) online planning worksheet. Both methods keep the cluster definition so after installing the necessary software packages recreation of the cluster itself should not last langer than about 60 seconds. From my personal experiences this always works as long as there are no configuration errors (logical glitches, reservation probs, violation of networking rules, changes with snmp to name a few). So I would create snapshot and OLPW file from cluster. Uninstall HA software, install HA Software. Reboot. Check storage and network. Recreate Cluster from (convertet) snapshot or OLPW whichever suits you more.
Also remember that you can use alt_disk_install to keep the current setup for easy/fast rollback. Needless to say that you do make a backup of every cluster node before you start.