Qlogic and Emulex Queue Length for EVA's

[darren franklin]

Does anyone have any details on the correct setting for Queue Length on Emulex and Qlogic HBA's when connecting to an EVA?
I cant find definative info regarding this anywhere.
Help appreciated
Darren

[IBaltay]

Hi,
there was the discussion on the perf counters queue length included in this thread:
http://forums11.itrc.hp.com/service/forums/questionanswer.do?admit=109447626+1225464283286+28353475&threadId=1239472

but the definite numbers probably dont exist and it always depends on the specific host/app/storage configuration and perf parameters...

[Uwe Zessin · Accepted solution]

The EVA can do up to 2048 outstanding I/Os on a single controller port (for all connected hosts), but the max. number on a single adapter port is way below it: 255.

As IBaltay has written, there is no single correct number. If there were, it would have been hard-coded. In most cases the default values are fine and it does not make sense to set the max. number on all servers.

This could cause an overrun on the storage array - some older boxes simply crashed and even the EVA has changed the response in a late VCS 3.0xx version to "Queue Full/Busy", because older host operating systems / device drivers did not handle it properly.

(While looking up some things for the text above I've came across an old customer advisory which recommends to limit or even not to change the queue depth when an online upgrade is to be done on an EVA3000/5000.)

[Amar_Joshi]

I assume you are talking about Windows and I am being specific Windows' Queue depth settings. Any other OS may behave differently.

HBA queue depth setting is fully depended upon configuration (Queue depth on Storage, LUN presentation per HBA etc.). A simple formula is:

Queue Depth = Target Queue Depth / Total number of LUNs mapped from the array


In Windows environment StorPort HBA drivers have changed important behavior about QD over SCSIPort drivers. StorPort drivers manages QD per LUN basis whereas SCSIPorts used to manage per target basis. Mentioned at:

http://download.microsoft.com/download/5/6/6/5664b85a-ad06-45ec-979e-ec4887d715eb/Storport.doc

Hope that I am not answering your question directly (since there is no direct answer) but helping you to understand it bit more.

My 2 cents worth.

[darren franklin]

thanks for all the assistance guys