On a SPARC based system with directly connected disks such as the IDE disks on an UltraSPARC system, the naming convention is the same as that for systems with bus-oriented controllers.
If you have only one controller on your system, w is usually 0.
For SCSI controllers, x is the target address set by the switch on the back of the unit, and y is the logical unit number (LUN) of the drive attached to the target. If the disk has an embedded controller, y is usually 0. For more information about SCSI addressing on SPARC based systems, see the SunSolve Info Doc 48041 and scsi_address(9S).
To indicate the whole disk, specify slice 2 (s2).