vmware – measuring iscsi write performance

I picked this trick up off vmware support. If you’ve got your iscsi all setup you can drop to the shell (either ssh or console) and do this to measure your average write throughput.

time vmkfstools -c 10G /vmfs/volumes/san_vmfs/my_vm/fat_disk.vmdk -d eagerzeroedthick

Try larger a larger disk if this is too quick (free space permitting)

Essentially this will initiate the host to create a fat disk in the location above. You will then get a time recorded on how long it takes to execute this command. Then you can use your maths skill to work out the transfer rate…

While this is happening you can open another SSH type esxtop then press “d” and watch the (d)isk throughput on the console. Pressing “v” will show you stats per (v)irtual machine.