Adaptec 131CA - AAA RAID Controller, Installation And Hardware Manual

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AAA-131CA Installation and Hardware Guide
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In general, use lower SCSI IDs for single disks; and use higher
SCSI IDs for drives used as array members or spares.
SCSI Termination
To ensure reliable communication on the SCSI bus, terminators must
be installed (or enabled) on the devices at the physical ends of each
SCSI channel. The terminators on all devices between the physical
ends must be removed (or disabled).
Terminating SCSI Channels on the AAA-131CA Adapter
Termination on the AAA-131CA adapter itself is controlled via the
SCSISelect utility. We recommend that you leave each channel on the
AAA-131CA adapter at its default setting of Auto Mode (the termina-
tors are enabled or disabled according to the SCSI connectors in
use). If you want to manually disable the AAA-131CA adapter ter-
mination setting, see Chapter 5, Configuring the AAA-131CA Adapter
with SCSISelect.
Terminating SCSI Devices
On most internal SCSI devices the termination setting is controlled
by setting a jumper or a switch, or by physically removing or
installing resistor modules. On most external SCSI devices,
termination is controlled by installing or removing a terminating
plug (see Figures 2-7 and 2-8). Read the device’s documentation to
determine how to enable or disable termination on your particular
SCSI device.
The internal SCSI cables supplied in the Adaptec AAA-131CA kits
have attached terminators, so you should disable termination on all
internal SCSI devices connected to the cable. In general, we recom-
mend that you terminate the internal cable instead of terminating
the SCSI devices. If you are using an array enclosure, we recom-
mend that you terminate the SCSI backplane or install an active ter-
minator on the second SCSI connector on the rear panel instead of
terminating the individual SCSI devices. If you follow these recom-
mendations, SCSI bus termination will not be affected when you
remove or replace SCSI devices.