American Megatrends MegaRAID Express 500 - Manual (Page 79)

Chapter 6 Hardware Installation 65
Step 8 Connect SCSI Cables , Continued
Cable Suggestions System throughput problems can occur if SCSI cable use is not maximized.
You should:
•
you can use cables up to 12 meters for LVD devices
•
for single ended SCSI devices, use the shortest SCSI cables (no more than 3 meters
for Fast SCSI, no more than 1.5 meters for an 8-drive Ultra SCSI system and no
more than 3 meters for a 6-drive Ultra SCSI system)
•
use active termination
•
avoid clustering the cable nodes
•
cable stub length should be no more than 0.1 meter (4 inches)
•
route SCSI cables carefully
•
use high impedance cables
•
do not mix cable types (choose either flat or rounded and shielded or non-shielded)
•
ribbon cables have fairly good cross-talk rejection characteristics
Step 9 Set Target IDs
Set target identifiers (TIDs) on the SCSI devices. Each device in a specific SCSI
channel must have a unique TID in that channel. Non-disk devices (CD-ROM or
tapes) should have unique SCSI IDs regardless of the channel where they are
connected. See the documentation for each SCSI device to set the TIDs. The
MegaRAID Express 500 controller automatically occupies TID 7 in the SCSI
channel. Eight-bit SCSI devices can only use the TIDs from 0 to 6. 16-bit
devices can use the TIDs from 0 to 15. The arbitration priority for a SCSI device
depends on its TID.
Priority Highest Lowest
TID 7 6 5
…
2 1 0 15 14
…
9 8
Important
Non-disk devices (CD-ROM or tapes) should have unique SCSI
IDs regardless of the channel they are connected to.