94 PCA-6157/6157L User's Manual
Using the Depth of Queue Tags Option
Command line option:
qdepth=<option>
Default value:
128
Valid options:
0-128
Function:
Set the depth of the queue for tag
command queuing. This value desig-
nates the depth of the queue per LUN
(I_T_L nexus), e.g. this value designates
the depth of the queue per device, or per
LUN, if a device has multiple LUNs.
Possible Impact:
Must be set to optimize the performance
of tagged command queuing.
Applicable Versions
3.04.00 and higher
This option is valid only when tag command queuing (qtags) has
been enabled. Values possible for this parameter range from 0 to
128. 0 is equivalent to qtags=disable. While the actual depth of the
queue depends on the specific drive controller, for single drives
values of about 10-30 are typically most optimal.
A greater number may be optimal for peripherals such as disk
arrays. Users should experiment with various qdepth values to
determine the most optimal performance of their particular setup.
The optimal qdepth value is based on different aspects of the
system, including but not limited to the processor, the available
memory, the disk drives, and other peripherals.
