The last weeks I’ve been working to get a VMware environment up and running in good shape. Since the hosts wouldn’t go into maintenance mode because the virtual machines couldn’t get migrated of the hosts. VMotion did actually work.
I decided to first take a run at updating the ESX3i hosts and Virtual Infrastructure Server 2.5 (they had U2 which had a known error).
After all the updates everything ran smoother, but still my little problem wasn’t solved. I guessed it must be due to DRS not working as it should.
I planned to remove all resource pools, since they were overly complex. After removing the resource pools I disabled HA and DRS. Then, after enabled it again, everything was OK and running. Host could be put into maintenance mode and everything went smooth as silk.
Since this all worked I moved on to updating the 2 other datacenters.
After some test runs with DRS and maintenance mode, I discovered that putting a host in maintenance mode stalled at 2% and nothing happened. It had gotten quite late and I was stressing my brain to figure this new problem out. It took me about an hour to check the DRS recommendations and saw the obvious answer: I put DRS to manual! DRS recommended to move all virtual machines to another host because the host was entering maintenance mode.
So this is just a reminder for myself: Don’t expect automatic behavior when you disable all automatic behavior…