The folks over at VMware’s performance team have posted an entry detailing how they got 350,000 IOPS at 8K 100% RANDOM I/O from the soon to be released vSphere 4 product.

http://blogs.vmware.com/performance/2009/05/350000-io-operations-per-second-one-vsphere-host-with-30-efds.html

They also talk about what they had to do with the previous version to get to 100,000 IOPS.