Benchmarking systems is one of the most important things you can do; amazing how many people don’t do it.  Benchmarking your disk subsystem is even more vital; even more amazing how many people don’t do it.

 

Why is benchmarking your disk subsystem so important?  Two reasons: firstly, so that when the day comes your system suddenly starts to go slowly you can more rapidly determine if it’s your disk subsystem is the problem.

 

Secondly, if you don’t know what throughput your disk subsystem can sustain, you won’t necessarily know what you’ve got is enough for your app.  Implied in this second point is that you need to ensure that your disk subsystem is running as it should.  I’ve used this tool effectively to show how two SANs, which I was assured were identical, were not (turned out the cache was different), saved a lot arguing.

 

SQLIO is a tool that’s freely downloadable to licensed SQL Server users that you can use to benchmark your disk subsystem and its available here:

http://www.microsoft.com/downloads/details.aspx?FamilyId=9A8B005B-84E4-4F24-8D65-CB53442D9E19&displaylang=en