what is the correct ‘lun-queue-depth’ setting for a XtremIO array if the target port has

Based on best practices, what is the correct ‘lun-queue-depth’ setting for a XtremIO array if
the target port has four LUNs and the ‘tgt-queue-depth’ is 256?

A.
256

B.
32

C.
64

D.
128