Most SCSI disks have embedded controllers. This means that the drive number will always be 0 but the target number varies. For example, if an external disk drive has its rear switch set to 2, the device name for the first slice is /dev/dsk/c0t2d0s0, not /dev/dsk/c0t0d2s0.
Because the names for SCSI targets 0 and 3 were reversed on some sun4c systems, device naming can be confusing. Under the SunOS 4.1.x software, SCSI target 3 was called sd0(), but it is now properly named c0t3d0. SCSI target 0 was called sd3(), but it is now named c0t0d0. Other SCSI disk names translate normally. For example, in the SunOS release 5.7 software, sd2a is c0t2d0s0 and sd2b is c0t2d0s1.