Dell PowerVault 775N (Rackmount NAS Appliance) - Manual (Page 22)

The only difference between cluster mode and joined-bus mode is the SCSI ID occupied by the enclosure services processor.
When cluster mode is detected, the processor SCSI ID changes from 6 to 15, allowing a second initiator to occupy SCSI ID 6.
As a result, SCSI ID 15 is disabled, leaving 13 available hard drives in cluster mode. As a result, you must remove the SCSI
ID 15 hard drive from the enclosure when using the enclosure in cluster mode.
Figure 2-5 illustrates the SCSI IDs and their associated hard drives for the PowerVault 22xS storage system.
Figure 2-5. PowerVault 22xS SCSI ID Numbers and Associated Drives
See your Dell PowerVault 220S and 221S Systems Installation and Troubleshooting Guide for more information about SCSI ID
assignments and cluster mode operation.
Table 2-3 provides a description of the split-bus module modes and functions.
Table 2-3. Split-bus Module Modes and Functions