VMWare 4.1 ISCSI Performance – Setting iops=1

I have recently ran across a setting in VMWare ESXi 4.1 that has improved total IOP’s across all my Virtual Machines (VM’s). Here is a CrystalDiskMark Result Before

Now after.

I’m not sure why the 512K reads have actually dropped, but what I can say is the total IOP’s are up across all VM’s.

Start by enableing remote tech support / SSH. Do this by going to Configuration tab / click Security Profile in the left nav / then click Properties in the top right of the window.

Open Putty and connect to the console.
Find the device names with the following command

esxcli nmp device list

Change IOPS from 1000 to 1 with the following command.

for i in `ls /vmfs/devices/disks/ | grep naa.600` ; do esxcli nmp roundrobin setconfig --type "iops" --iops=1 --device $i ;done

You might need to change the grep command. For example, an Openfiler box starts with t60.F40 instead of naa.600 like the Windows Storage servers.