Still no info on ESX versions :/, i'm trying to get intouch with the wm people.

Side by Side - Yepp 2 clusters and move system by system takes time but its a safe method.

However it seems like i have to do this fast (i dont like shooting fast ...) since the virtual isn't performing accaccording the SLA we have to mak a fast solution,

I think i will use the solution where i bring up a second cluster backup/restore on the new cluster, bring down the old, rename the new.

I did a similar thing a few days ago on a single sql2008r2 with 6 instances, a few small hickups due to high security thinking with accounts and so other than that it went more smooth then i expected it to do.

The only thing was the naming in active directory, where we had to delete the server and register the new again...

Thanx to all of you who respond and discuss....

I will update here when the job is done and post the results for others to read. (Job has to be done in 3-4 weeks.)