Manualshelf

Technical data

ManualsBrandsCompaq ManualsHome building and DecorStorageWorks TM RAID Array 3000 Pedestal Storage Subsystem
71727374757677787980
After the host adapter has been serviced, if there are still SCSI IDs retained
from the previous arbitration cycle, the next highest SCSI ID is serviced.
When all devices in the group have been serviced, the DS-DWZZH-05
repeats the sequence at the next arbitration cycle.
Fair arbitration is disabled by placing the switch on the front of the
DS-DWZZH-05 UltraSCSI hub in the Disable position. (See Figure 3–4.)
With fair arbitration disabled, the SCSI requests are serviced in the
conventional manner; the highest SCSI ID asserted during the arbitration
cycle obtains use of the SCSI bus.
______________________ Note _______________________
Host port SCSI ID assignments are not linked to the physical port
when fair arbitration is disabled.
The DS-DWZZH-05 reserves SCSI ID 7 regardless of whether fair
arbitration is enabled or not.
3.6.1.2.3 DS-DWZZH-05 Address Configurations
The DS-DWZZH-05 has two addressing modes: wide addressing mode and
narrow addressing mode. With either addressing mode, if fair arbitration is
enabled, each hub port is assigned a specific SCSI ID. This allows the fair
arbitration logic in the hub to identify the SCSI ID of the device participating
in the arbitration phase of the fair arbitration cycle.
_____________________ Caution _____________________
If fair arbitration is enabled, the SCSI ID of the host adapter
must match the SCSI ID assigned to the hub port. Mismatching
or duplicating SCSI IDs will cause the hub to hang.
SCSI ID 7 is reserved for the DS-DWZZH-05 whether fair
arbitration is enabled or not.
Jumper W1, which is accessible from the rear of the DS-DWZZH-05 (see
Figure 3–3), determines which addressing mode is used. The jumper is
installed to select narrow addressing mode. If fair arbitration is enabled, the
SCSI IDs for the host adapters are 0, 1, 2, and 3. (See the port numbers not
in parentheses in Figure 3–4.) The controller ports are assigned SCSI IDs 4
through 6, and the hub uses SCSI ID 7.
Shared SCSI Bus Requirements and Configurations Using UltraSCSI Hardware 3–13