An administrator receives a complaint that a virtual machine is performing poorly.
The user attributes the issue to poor storage performance. If the storage array
Is the bottleneck, which two counters would be higher than normal? (Choose two)
A.
Average device latency per command, in milliseconds(DAVG per cmd)
B.
Average ESXi VMKernel latency per command, in milliseconds (KAVG per cmd)
C.
Average virtual machine operating system latency per command, in milliseconds (GAVG per cmd)
D.
Number of SCSI reservation conflicts per second (CONS per second)
Explanation:
http://www.yellow-bricks.com/esxtop/
A & D is Correct
Kernel command latency(B) & Physical device command latency(A).
Reference: Vmware vSphere 5: Install, Configure, Manage.
CMDS/s This is the total amount of commands per second and includes IOPS (Input/Output Operations Per Second) and other SCSI commands such
as SCSI reservations, locks, vendor string requests, unit attention commands etc. being sent to or coming from the device or virtual machine being monitored.
In most cases CMDS/s = IOPS unless there are a lot of metadata operations (such as SCSI reservations)
DAVG/cmd This is the average response time in milliseconds per command being sent to the device
I would say A and B if just pertaining to the Storage Array.
KAVG/cmd This is the amount of time the command spends in the VMkernel
GAVG/cmd This is the response time as it is perceived by the guest operating system. This number is calculated with the formula: DAVG + KAVG = GAVG
If the problem is array would you check esx eq vmkernel latency or maybe array stats eq device latency per command and if overloaded array with scsi conflicts – locks on vmfs this could degrade performance at the array lvl