Technical data

54
CONTROL SOFTWARE FOR SCSI EXTENDER AND SWITCHES
14. SCSI Installation Tips
Keep your SCSI chain short. Official SCSI specifications limit a SCSI single-ended
chain to no more that 6 meters (19.7 feet) long. Practical experience says the
shorter, the better. The maximum length you should allow between devices is
3 feet.
Never assign the same SCSI ID number to two devices on the same bus. SCSI uses
these numbers as addresses to ensure that information goes to the correct location.
Giving two devices the same address can result in lost information.
Know that some SCSI-ID numbers may be reassigned. Internal boot hard drives are
usually set to ID “0,” while secondary hard drives are set to “1”. Motherboards or
host adapters are generally set to ID “7”.
Always terminate the first and last devices on the chain. Drives purchased
specifically for internal use nearly always arrive with terminators installed. If in
doubt, call the vendor that you purchased a device from.
If the last device on the chain has two SCSI connectors, attach the cable to one and
a terminator to the other. Otherwise, you’ll have an open connector that may cause
noise on the SCSI chain.
Always turn off the power to your computer and SCSI devices before swapping
cables or moving devices around. SCSI cables contain sensitive data transmission
lines and one or more live power wires.
Turn on your SCSI devices before you turn on the computer. Some SCSI devices
will not mount if they are not running when you power up your computer.
Shutting down your computer first and then the attached SCSI devices allows your
system to completely “flush” itself.