Setting the queue depth for an HP-UX host

This section describes the formula and the procedure for setting the queue depth.

Before you set the queue depth, you must attach the host system to a DS6000™. See Hewlett-Packard Server (HP-UX) host attachment for instructions on connecting a host to a DS6000

Follow these steps to set the queue depth.

Use the following formula to set the queue depth for all classes of HP-UX:
256 ÷ maximum number of LUNs = queue depth

Note: Although this algorithm implies that the upper limit for the number of LUNs on an adapter is 256, HP-UX supports up to 1024 LUNs.
You must monitor configurations with greater than 256 LUNs. You must adjust the queue depth for optimum performance.
To update the queue depth by device level, use the following command: scsictl -m queue_depth=21 /dev/rdsk/$dsksf
where /dev/rdsk/$dsksf is the device node.
To make a global change to the queue depth, use the HP System Administration Manager (SAM) to edit the kernel parameter so that it equals scsi_max_qdepth.