As you will see from the diagram below, this particular VMware installation is using a Software ISCSI initiator (vmhba38)

Key:

CMDS/s – Number of IOPS per second (READ/s + WRITE/s) and other SCSI commands such as SCSI locks, reservations, etc. These are normally nominal though compared to IOPS.

MBREAD/s & MBWRTN = Self explanatory (in MegaBytes)

DAVG/cmd = Average response (in ms) per command being sent to the device

KAVG/cmd = Amount of time spent in the VMKernel. This should be to close to 0.00 as possible.

GAVG/cmd =  This is the response time that is perceived from the Guest OS. (KAVG/cmd + DAVG/cmd)

 

Now the big question. What DAVG/cmd  and GAVG/cmd values should we start worrying about? Common consensus suggests anything constantly over 30ms then you’ll start seeing applications slow down. The odd spike is common but anything averaging below 20-30 ms is fine.

Further information on esxtop: http://communities.vmware.com/docs/DOC-9279