We have a Dell R710 that had serious hardware issues last Friday evening. Dell replaced the mobo and processor, and the machine booted fine. The server runs Win2k8 R2 Server Core, and hosts 4 VMs, all Win2k8 R2. One of the VMs runs SQL Server 2008 R2. Storage is RAID10 SAS 15k.
I have a few benchmark queries for SQL server that take about 30 seconds to run. After the repairs from Friday, they now take about 60 seconds to run. I can't figure out what's causing the drop in performance. The configuration for everything has not changed, only the mobo and processor. Any ideas on what I should be looking at?
Are you sure the bios is configured correctly ? Most default bios configs on motherboards ship with Hyper-threading and VT-x disabled. That just might make all the difference, especially with VM's. Also possible that the bios on the new board is an old version and doesn't recognize a new CPU properly causing it to run at lower frequencies.
Of course they could really have saddled you with a slower CPU than you used to have.
Don't believe what Windows is telling you about the CPU and the speed. This could be totally bogus. (Either because Windows doesn't know about this particular model CPU or because it hasn't realized there was a CPU change and it is happily reporting the values from the previous CPU.)
Use CPU-z: This will always pull the info from the CPU itself and tell you what is really there in much greater detail than Windows.
I would say look at the standard set of performance counters you look at whenever you are baselining SQL Server (Brent Ozar has a good post about SQL Server performance counters).
Look at system utilization. Hopefully you have before pictures as well to compare against. If not, look for resources that appear to be bottlenecks.
I would also look at the server logs to ensure all things are running at their best, both on the host and the guest. Look at the hardware logs and the manufacturer's open manage/power manage/etc. tools.