Additional Hints For Connecting Scsi Devices - Adaptec AAA-130U2 Installation And Hardware Manual

AAA-130U2 Series Installation and Hardware Guide

Additional Hints for Connecting SCSI Devices

All SCSI Devices
If you are booting your system from a single SCSI hard disk or
bootable array, the boot order (or virtual device order) of the
hard disk or array must be set to 0. (See Making the Array Boota-
ble on page 3-8.)
Enable termination power on all SCSI devices in the system so
that if you remove a drive that is supplying termination power
other devices will still provide it.
Symptoms of SCSI cabling-related problems are drives not
being recognized, drives locking up, or drives that deactivate.
Use good-quality SCSI cabling, and minimize the stub lengths.
Good-quality cables should not be limp when you pick them
up. (See Appendix D, Obtaining SCSI Cables for additional
information.)
Cable Lengths
The total length of cabling (internal and external) on each SCSI
channel may not exceed the maximum lengths listed in the
following table:
Maximum Cable Lengths for each SCSI Channel
Maximum
Cable Length Data Transfer Rate
12 m (29.4 ft) Ultra2 (80 MBytes/sec)
3 m (9.8 ft) Fast SCSI
(10 MBytes/sec)
3 m (9.8 ft) Wide SCSI
(20 MBytes/sec)
3 m (9.8 ft) Ultra SCSI
(40 MBytes/sec for 16-bit (Wide),
20 MBytes/sec for 8-bit)
1.5 m (4.9 ft) Ultra SCSI
(40 MBytes/sec for 16-bit (Wide),
20 MBytes/sec for 8-bit)
1
Mixing Fast/Ultra devices with Ultra2 devices on the same channel causes the
channel to default to Ultra SCSI speeds and cable requirements.
2
Ultra SCSI data transfer rates do not currently support more than eight devices.
2-8
Maximum
Devices
Supported
1
15
7
15
4
2
5-8