Avago Technologies MegaRAID SCSI 320-0 (520-0 CH) - Manual (Page 31)

Detailed Installation 2-7
Copyright © 2003-2008 by LSI Corporation. All rights reserved.
System throughput problems can occur if SCSI cables are not
the correct type. To minimize the potential for problems,
– use cables no longer than 12 meters for Ultra160 and
Ultra320 devices (it is better to use shorter cables,
if possible)
– use the shortest SCSI cables for SE SCSI devices
(no longer than 3 meters for Fast SCSI, no longer than
1.5 meters for an 8-drive Ultra SCSI system, and no
longer than 3 meters for a 6-drive Ultra SCSI system)
– use active termination
– avoid clustering the cable nodes
– note that the cable stub length must be no greater than
0.1 meters (4 inches)
– use high impedance cables
– route SCSI cables carefully.
Step 7. Set SCSI Termination
The SCSI bus is an electrical transmission line and must be
terminated properly to minimize reflections and losses. Set
termination at each end of the SCSI cable(s).
For a disk array, set SCSI bus termination so that removing or
adding a SCSI device does not disturb termination. An easy
way to do this is to connect the Storage Adapter to one end of
the SCSI cable and to connect an external terminator module
at the other end of the cable. You can then connect SCSI disk
drives to the connectors between the two ends of the cable. If
necessary, disable termination on the SCSI devices. (This is not
necessary for Ultra320 and Ultra160 SCSI drives.)
Set the termination so that SCSI termination and TermPWR are
intact when any disk drive is removed from a SCSI channel, as
shown in
Figure 2.3 .