sunos4 disk devices were named like xy0a or xd2h or sd1b. the first 2 letters were the controller (xy/xd were different types of xylogics smd controllers, sd sc

sunos4 disk devices were named like xy0a or xd2h or sd1b. the first 2 letters were the controller (xy/xd were different types of xylogics smd controllers, sd scsi), the number was the unit number, and the letter was the partition, with some fairly strong conventions (a=root, b=swap, c=whole disk, d..h=other)