So you’ve heard this probably from a few dozens of people by now when you don’t hit the expected SAN performance: Set your queuedepth to a larger size.
So how do you set this queuedepth? Find out for which module you’ll need to set this option:
vmkload_mod -l | grep qla
Now set it to a depth of 64 for module qla2300_707
esxcfg-module -s ql2xmaxqdepth=64 qla2300_707
esxcfg-boot –b
So now you’ve set the queue depth to 64 for your HBA cards, but why? Well I hope the answer is:”because I monitored my system with esxtop and I noticed that the “QUED” value was high”.
So there’s your when. You’ll need to set this setting if you notice a high “QUED” value in esxtop. Take a look at the following example I borrowed from a great blog on this subject:
As you can see in the example, the “ACTV” has a value of 32. Indeed 32 active commands cause that’s the default queue depth for qlogic cards. And 31 outstanding commands, in other words if we bump up the queue depth to 64 than all the commands should be processed instead of queued in the VMkernel.
What will this result in?
Brent Ozar says
You should also check your fiber switch metrics for errors, because you’re probably causing collisions. Cranking up the queue depth too far can mean cranking up the error numbers.
tgreat says
Hi, what can I do if there is no data in columns ACTV/QUED/%USD/LOAD (there is a “-” sign there instead) ?
Duncan Epping says
Start with the following: S 2 (this means refresh the data every 2 seconds)
AlexB says
@tgreat: Have the same Problem
@ Duncan: Did not work for the colums ACTV/QUED/%USD/LOAD …
Any solution?
Duncan Epping says
I am going to look into this, see if I can find any related problems… can’t promise anything though cause I’m not able to reproduce this it’s hard to troubleshoot.
AlexB says
Got it!
Open esxtop
Press “d” for Disk Statistics
Press “v” to display the storage system information per virtual machine
or
Press “u” to display the information per storage device.
Found the information on the technical note from VMware about “Perfomance Analysis Methods”
JasonD says
I assume this problem also applies to ESXi? How would you increase the q-len on that platform?