I regularly use SQLIO.EXE to gauge the maximum throughput a disk subsystem can sustain. Recently Microsoft released SQLIOSIM.EXE to provide better results for this type of test. However they didn't release any documentation on the tool and I could never figure out what it was trying to tell me. It looks like they finally did release a Knowledge Base article on SQLIOSIM. Give it a spin. I'd be curious to hear what you think of the tool.