Tuesday, December 15, 2009

Virtualization – final wrapup

This is another topic I want to wrap up before the end of the year.

A quick overview. earlier this year, I did some testing of virtualizing our production servers hosted on VMWare servers. I captured a typical workload from our busiest server and replayed it on servers set up for testing; a 32-bit physical server with 16 CPU set up as a production server, the same server with hyper threading turned off, a 32-bit and a 64-bit virtual server with 4 CPUs,and a 32-bit and a 64-bit virtual server using vSphere and 8 CPUs. All servers had 16 GB of RAM.

After running the workload multiple times on each server configuration we compared results. What we saw was understandable – neither the 4 CPU or 8 CPU servers matched the 16 core baseline. Even the physical server with HT off fell short.

What I didn’t show in earlier posts was the counter for latches. Latches are the #1 wait type on our servers, and this held true on all testing servers. Our servers aren’t running optimized and this is being magnified in a virtual environment. Having 16 cores lessens the performance hit from all those latches in production.

So we’re not going to virtualize,at least the production servers. While virtualization is useful and can be used for SQL, it’s not a good idea to try and virtualize servers with performance problems. We’re currently using VMWare to run our development and testing environments as well as a few smaller, less used SQL servers, and we’re not seeing any issues with them.

I’m not going to published a summary of all my counters, but I’ll make them available on request if anyone is interested.

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