Via the Dutch VMUG site I landed on a new blog, well new… for me new. This blog is maintained by Toni Verbeiren and he created an excellent article about monitoring performance stats for the scsi controllers inside a VM:
A tool is available on ESX 3.5 that creates histograms by default (and complete traces if wanted) is VscsiStats. As an option, one provides the vSCSI handle ID and the VM World ID. In order to get some statistics at all, one first needs to start the monitoring:
./vscsiStats -sAfter some time, the relevant statistics can be fetched by issuing a command like:
./vscsiStats -i 8260 -w 1438 -p ioLength
There also appears to be a pdf about the subject on the VMware website which contains good information on the subject.
EDIT: You can find the command here: /usr/lib/vmware/bin