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SCSI Bus Termination
When a SCSI-to-SCSI configuration exists, there are essentially two SCSI buses
present: the host SCSI bus and the drive SCSI bus.
Host SCSI Bus
The host SCSI bus consists of the host bus adapter, the data cable, the S2S
Interface card, and the Ultra S2S RAID Controllers' host channel SCSI I/O
processor. SCSI bus termination is required on the host SCSI bus and occurs
at the host bus adapter and on the last S2S Interface card on the SCSI bus.
Since multiple CR8e subsystems can be daisy-chained together through this
host SCSI bus, SCSI termination will need to be enabled only on the last S2S
Interface card on the bus. A jumper located on the S2S Interface card (JP1) is
removed to enable SCSI bus termination when the card is the last device in
the SCSI bus chain (off-set one pin to act as a hold for the jumper). For
multiple cabinets disable SCSI bus termination on the interim S2S Interface
cards by installing the jumper at JP1 and terminating the last S2S Interface
card in the chain (removing jumper).
Drive SCSI Bus
The drive SCSI bus consists of the Ultra S2S RAID Controller's disk channel
0 and 1 SCSI I/O processors, the backplane circuitry, the disk drives, and the
I/O Interface card. If there are multiple cabinets connected in a master/slave
configuration, the drive SCSI bus includes all cabinet drives, backplane
circuitry, data cables, Ultra Extender cards, and I/O Interface cards.
The Ultra S2S RAID Controller supports active termination providing a
stable quality SCSI termination signal. Drive SCSI bus termination is
provided automatically by either the Ultra Extender or I/O Interface cards
and requires no user intervention. The Ultra Extender and I/O Interface
cards are designed to sense whether they are the last device on the SCSI bus
and if so, automatically self terminate.
Introduction
5
SCSI Functions
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