We've been experiencing strange issues for awhile now with our virtual environment running SQL Servers.
We randomly get calls from users about very poor performance on the SQL boxes. Sure enough when I look I see the CPUs are pegged at 100%. I perform a VMotion to another host and as soon as it finishes moving over to another host performance immediately returns to normal.
I've been working with the VMWare admins and they have assured me that VMotion would not affect anything on the SQL Servers. It's almost as if the move to another host is causing an execution plan change or the like. I don't understand, however, why out of nowhere CPU usage jumps through the roof unless it's a bad query plan recompile due to parameter sniffing, but I would think that a VMotion would not fix that since it's supposed to be transparent.
The VM farm is comprised of 19 Dell servers (sorry I don't know the exact model) with 2 physical sockets and 12 cores on each socket.
Has anyone else observed this behavior before? I'm wondering if it's something to do with capacity as there are some large VMs for the hosts to handle it seems (there are 14 80GB, 12 core VMs floating around). Even with those VMs on the farm I can see in the Vsphere console that the hosts aren't being over-utilized (memory does creep up to the 80% mark a lot of the time, but no ballooning).
Also, this occurs on all different versions of SQL (2008, 2008R2, 2012, and 2014).
Thanks a lot for any insight!