Adaptec AAA-130U2 SERIES, Руководство по оборудованию, Страница: 22 / 82

2-8
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
Maximum
Devices
Supported
12 m (29.4 ft) Ultra2 (80 MBytes/sec)
1
1
Mixing Fast/Ultra devices with Ultra2 devices on the same channel causes the
channel to default to Ultra SCSI speeds and cable requirements.
15
3 m (9.8 ft) Fast SCSI
(10 MBytes/sec) 7
3 m (9.8 ft) Wide SCSI
(20 MBytes/sec) 15
3 m (9.8 ft) Ultra SCSI
(40 MBytes/sec for 16-bit (Wide),
20 MBytes/sec for 8-bit) 4
1.5 m (4.9 ft) Ultra SCSI
(40 MBytes/sec for 16-bit (Wide),
20 MBytes/sec for 8-bit) 5-8
2
2
Ultra SCSI data transfer rates do not currently support more than eight devices.