Setting SCSI IDs

You must assign the SCSI host bus adapter and each SCSI device a separate SCSI ID (0 through 15 for a 16-bit SCSI bus). The device's priority on the SCSI bus is determined by the device's SCSI ID. The order of SCSI ID priorities (from highest to lowest) is 7, 6, 5, 4, 3, 2, 1, 0, 15, 14, 13, 12, 11, 10, 9, and 8. A device with SCSI ID 7 has the highest priority, and one with SCSI ID 8 has the lowest.

When you are assigning SCSI IDs, we recommend you give the SCSI host bus adapter higher priority than the other SCSI devices on the bus. SCSI ID 7 is the preset SCSI ID for the A5159B SCSI host bus adapter (giving it the highest priority on the SCSI bus). Set each of the other SCSI devices on the bus to one of the remaining SCSI ID's.

For a multi-initiator (High Availability [HA]) configuration—where multiple SCSI host bus adapters are connected to the same SCSI bus—the SCSI host bus adapter that carries the most traffic should be assigned a SCSI ID of 7 (giving it the highest priority), then you must change the SCSI ID of each of the remaining SCSI host bus adapter's on the bus from the preset setting (7), to the next highest priority remaining SCSI IDs (e.g. 6, 5, 4... and so on).

If you plan to boot your system from a hard disk drive on the SCSI bus,you should assign that drive the next highest priority unassigned SCSI ID. If there is only one SCSI host bus adapter (SCSI ID = 7), the hard disk drive would be assigned a SCSI ID of 6. If there are multiple SCSI host bus adapters, the hard disk drive would be assigned the next highest priority SCSI ID available after all of the SCSI host bus adapters have been assigned higher priority SCSI IDs.

To change the A5159B host bus adapter's SCSI ID, refer to “Checking SCSI Bus Compatibility”.

The peripheral device SCSI IDs are usually set with jumpers or a switch on the peripheral. Refer to the peripheral manufacturer's instructions to determine the ID of each device and how to change it.

	IMPORTANT: You must have no duplication of SCSI IDs on a SCSI bus—the system will hang or crash if duplicate SCSI IDs are on the bus.

Make any necessary changes to the SCSI IDs and record the IDs for future reference. You can use Table 2-5 “Record of SCSI IDs” below to keep a record of the IDs