I have an 2010 27" iMac with an SSD and a regular hard drive. Now that I've been using the machine for some time and have not come close to filling the SSD, I'd like to disable the spinning hard drive completely. Why? It makes a loud humming sound when it runs, and I don't use it for anything. Anything I can do short of taking apart this monster and ripping it out?
UPDATE: As of 3-Apr-2012 and OS X 10.7.3, the solution below works. Some programs occasionally spin up the drive, but it only hums for about 5 minutes then goes back to sleep.