scsictl and queue_depth parameter

[Pablo Esteban Arnaldi]

Hi!
We have a couple of EVA5000 with superdome running 11.11.
I like to know what could change if I use de scsictl command to increase de queue_depth parameter. The default value for this parameter is 8 but I don´t really understand how it works. 8 means that de OS sends 8 scsi commands in parallel to the controller? Can I increase the performance if I increase to 16? Somebody knows how this impacts in the EVA controllers? Thanks in advance, and best regards to all.
Pablo

[Peter Mattei]

Hi
Increasing the queue size will allow more IOs to be queued thus allowing to make the array more busy.
The total of outstanding IOs from all attached hosts to an EVA should not be >2048.
To get the number just add all IO_Queues of all attached Hosts (HBAs)
Also read this support document. It is also very valid for the EVA.
http://h20000.www2.hp.com/bizsupport/TechSupport/Document.jsp?objectID=lpg35039

Cheers
Peter