Technical data

Table 3–1: SCSI Bus Speeds
SCSI Bus Transfer Rate (MHz) Bus Width (Bytes)
Bus Bandwidth
(Speed) MB/sec
SCSI
515
Fast SCSI
10 1 10
Fast-Wide
10 2 20
UltraSCSI
20 2 40
UltraSCSI-II
40 2 80
3.3 SCSI Bus Device Identification Numbers
On a shared SCSI bus, each SCSI device uses a device address and must
have a unique SCSI ID (from 0 through 15). For example, each SCSI bus
adapter and each disk in a single-ended storage shelf uses a device address.
SCSI bus adapters have a default SCSI ID that you can change by using
console commands or utilities. For example, a KZPSA adapter has an initial
SCSI ID of 7.
______________________ Note _______________________
If you are using a DS-DWZZH-05 UltraSCSI hub with fair
arbitration enabled, SCSI ID numbering will change. (See
Section 3.6.1.2.)
Use the following priority order to assign SCSI IDs to the SCSI bus adapters
connected to a shared SCSI bus:
7-6-5-4-3-2-1-0-15-14-13-12-11-10-9-8
This order specifies that 7 is the highest priority, and 8 is the lowest priority.
When assigning SCSI IDs, use the highest priority ID for member systems
(starting at 7). Use lower priority IDs for disks.
Normal SCSI priority is not followed when using the DS-DWZZH-05
UltraSCSI hub with fair arbitration enabled because the DS-DWZZH-05
determines the SCSI ID of the next device to use the SCSI bus.
The SCSI ID for a disk in a BA350 storage shelf corresponds to its slot
location. The SCSI ID for a disk in a BA356 or UltraSCSI BA356 depends
upon its slot location and the personality module SCSI bus address switch
settings.
3–6 Shared SCSI Bus Requirements and Configurations Using UltraSCSI Hardware