Additional Hints For Connecting Scsi Peripherals - Adaptec AAA-130SA SERIES Installation And Hardware Manual

AAA-130SA Series Installation and Hardware Guide

Additional Hints for Connecting SCSI Peripherals

All SCSI Peripherals
If you are booting your server from a single SCSI hard disk
drive or bootable array, the boot order (or virtual device order) of
the disk or array must be set to 0. (See Making the Array Bootable
on page 3-5.)
Enable termination power on all SCSI peripherals in the server
so that if you remove a drive that is supplying termination
power other peripherals 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 E, Obtaining SCSI Cables and Converters for
additional information.)
Cable Lengths
The total length of cabling (internal and external) on each SCSI
channel should not exceed the following:
– Three m (9.8 ft) if you are using Fast SCSI data transfer
rates (10 MBytes/sec).
– Three m (9.8 ft) if you are using Ultra SCSI data transfer
rates (20 MBytes/sec for 8-bit peripherals, and 40 MBytes/
sec for 16-bit peripherals) and have four or less peripherals
(including the Array controller).
– One and one-half m (4.9 ft) if you are using Ultra SCSI data
transfer rates and have between four and eight peripherals
(including the Array controller).
Note:
support more than eight peripherals per channel.
– Six m (19.7 ft) if you are using 5-MByte/sec asynchronous or
synchronous data transfer rates.
When calculating the total length of the bus, be sure to include
the cabling inside any array enclosure.
2-8
Ultra SCSI data transfer rates do not currently