Dell PERC 4/DC - Manual (Page 15)

Step 6 Set Target IDs
Set target identifiers (TIDs) on the SCSI devices. Each device in a channel must have a unique TID. Non-disk devices 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 RAID controller automatically occupies TID 7, which is
the highest priority. The arbitration priority for a SCSI device depends on its TID.
Table 3 -4 lists the target IDs.
Table 3-4. Target IDs
Step 7 Set SCSI Termination
The SCSI bus is an electrical transmission line and must be terminated properly to minimize reflections and losses. Termination should be set 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
RAID controller to one end of the SCSI cable and an external terminator module at the other end of the cable, as shown in
Figure 3 -6 .
The connectors between the two ends can connect SCSI drives which have their termination disabled, as shown in the drives (ID0, ID1, ID2) attached in the
figure. See the documentation for each SCSI drive to disable termination.
Set the termination so that SCSI termination and TermPWR are intact when any hard drive is removed from a SCSI channel.
Figure 3-6. Terminating Internal SCSI Disk Array
NOTE: The RAID controller can occupy TID 6 in cluster mode. When in cluster mode, one controller is TID 6 and the other TID 7. IDs 0 - 7 are valid target
IDs; 7 has the highest priority.
Priority Highest Lowest
TID 7 6 5 ... 2 1 0 15 14 ... 9 8
NOTE: Dell does not recommend mixing U160 and U320 drives on the same bus or logical drive.