How to measure disk performance?

I always use HDTune. Simple, 'fast' and you can compare test results on their website.

IOMeter is great for measuring disk performance, there are several sites available that carry reference tables (I used one for VMWare based PC's, so I suggest you google for alternatives :-) )

EDIT: Found a very nice table on Tom's Hardware, I'm guessing the "workstation" profile seems to fit quite well...

ATTO Disk Benchmark.

The ATTO Disk Benchmark performance measurement tool measures storage systems performance with various transfer sizes and test lengths for reads and writes. Several options are available to customize your performance measurement including queue depth, overlapped I/O and even a comparison mode with the option to run continuously.