Intel
®
SRCU41L Raid Controller User Manual
9
Hardware Installation
7. Connect SCSI Devices to the Storage Adapter
Use SCSI cables to connect SCSI devices to the Intel
®
Raid Controller SRCU41L.
To connect the SCSI devices
a. Disable termination on any SCSI device that does not sit at the end of the SCSI bus.
b. Configure all SCSI devices to supply TERMPWR.
c. Connect cables to the SCSI devices. See the following table for maximum cable lengths.
You can connect up to 15 Ultra SCSI devices to each SCSI channel.
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’s 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 meter (4 inches)
— use high impedance cables
— route SCSI cables carefully.
8. 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 Intel
®
Raid Controller SRCU41L
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 4.
Table 3. Maximum Cable Length
Device
Cable Length in Meters
Fast SCSI (10 Mbytes/s)
3
SE SCSI
3
Ultra SCSI
1.5
LVD
12
