This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
From the Apple IIgs Owner's Reference, page 267: "In order for the Finder to recognize a hard disk, the hard disk must be switched on and up to speed before you start up (or restart) the computer. Switch on the hard disk, wait about 10 seconds for it to come up to speed, and then restart the computer." From the Macintosh User's Guide for desktop Macs, page 216: "IMPORTANT: Always turn on any external SCSI devices connected to your Macintosh before turning on the computer itself. Otherwise, your computer cannot recognize the SCSI devices." By: B.J. Major ___________________________