Recently I had a performance tuning gig at a customer reporting that despite having the same number of vCPUs configured into the Logical Domain, the performance of both systems was different. A further observation was that a significant number of CPUs weren’t used on that system.
I just want to share something that I've learned a few days ago by doing this. Let's assume you have a ZFS pool. 1 TB in size. You want to add some storage. By accident you grab a slice 0 that is 128MB large instead of the whole LUN. The obvious question is how do you get rid of it. You may get to the idea that you replace the 128 MB LUN with a 1 TB LUN. We do this replacement all the time to increase of rpools. However: For the given situation this is an exceptionally bad idea.