HP I Dual Channel Ultra160 SCSI Host Adapter A6829A manual Performance Tuning

Installing the A6829A Adapter

Performance Tuning

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).

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