Set queue depths on HP-UX hosts


You can change the LUN or device queue depth on HP-UX hosts using the kernel parameter scsi_max_qdepth. You can change the HBA queue depth using the kernel parameter max_fcp_reqs.

  • The default value for scsi_max_qdepth is 8. The maximum value is 255.

    scsi_max_qdepth can be dynamically changed on a running system using the -u option on the kmtune command. The change will be effective for all devices on the system. For example, use the following command to increase the LUN queue depth to 64:

    kmtune -u -s scsi_max_qdepth=64

    It is possible to change queue depth for individual device files using the scsictl command. Changes using the scsictl command are not persistent across system reboots. To view and change the queue depth for a particular device file, execute the following command:

    scsictl -a /dev/rdsk/c2t2d0

    scsictl -m queue_depth=16 /dev/rdsk/c2t2d0

  • The default value for max_fcp_reqs is 512. The maximum value is 1024.

    The kernel must be rebuilt and the system must be rebooted for changes to max_fcp_reqs to take effect. To change the HBA queue depth to 256, for example, use the following command:

    kmtune -u -s max_fcp_reqs=256