Qlogic retry interval

I posted earlier about a test with the XIV with where the retry interval was too high and IO was queued longer than it had to be on the system buffer as opposed to being written to disk (see graph). We solved this a while ago, but I forgot to post an update.

Qlogic cards have an on-board BIOS setting, which sets the path failure delay to 45 seconds. In order for multipath to perform properly on these systems, this limit should be lowered. We're currently setting the limit to 0. The options to find in the BIOS are under the advanced settings for each host controller.

You should also set the following in in /etc/modprobe.conf (Fedora/RedHat/CentOS) or /etc/modprobe.d/aliases (Debian/Ubuntu):

options qla2xxx ql2xfailover=0 
options qla2xxx qlport_down_retry=1
options qla2xxx ql2xmaxqdepth=64

Note that the maxqdepth setting on the third line isn't about fail over but about getting more IOPS with respect to the queue depth. This is a standard XIV tuning practice. If you're using Emulex cards you can set the queue depth to 64 with the following line in your modprobe configuration file:

options lpfc lpfc_hba_queue_depth=64

but it is not necessary to change a retry or failover interval.