HP A6829A PCI Dual Channel Ultra160 SCSI Host Bus Adapter Service and User Guide (May 2003)

Installing the A6829A Adapter

Performance Tuning

Chapter 2 13

Performance Tuning

To get the best performance from the A6829A adapter, we recommend

the following things:

• Increase the number speciﬁed for the scsi_max_qdepth kernel

tunable parameter:

— HP-UX 11.0: scsi_max_qdepth is a static tunable that you can

change in SAM (“Kernel Conﬁguration” screen → “Conﬁgurable

Parameters” screen). Note that because this is a static tunable,

you will need to reboot the system after changing its value.

— HP-UX 11i: scsi_max_qdepth is a dynamic tunable, so no

system reboot is needed to change the parameter’s value. See

“SCSI Queue Depth Management” in the HP-UX 11i Release

Notes for more information about this tunable.

If you see “queue full” messages in the /var/adm/syslog.log ﬁle,

you can avoid those messages by reducing the value for

scsi_max_qdepth.

• Install the A6829A adapter in a PCI4X slot in the HP-UX system.

• Do not put any Single Ended (SE) SCSI devices on the same SCSI

bus as Low Voltage Differential (LVD) SCSI devices. Doing this

changes the entire bus to SE, which limits the bus to Ultra SCSI (40

MB/s).

• When you are assigning SCSI IDs to the SCSI devices on the bus,

consider giving those devices the higher priorities on the bus (SCSI

ID 7 is usually assigned to the HBA). See “SCSI IDs” on page 27 for

more information.

• Ensure to set the adapter’s maximum data transfer rate to the

correct rate (see “Maximum Data Transfer Rate” on page 29 for more

information).

• Ensure to have the correct SCSI hardware conﬁguration. Domain

Validation can detect some conﬁguration problems (see “Domain

Validation” on page 100).