If part of your backup strategy includes cloning your Mac’s hard drive using a tool such as SuperDuper or CarbonCopyCloner, you’ll want to make sure that Spotlight isn’t active on that drive before you start cloning to it.
By default, Spotlight indexes everything it finds, anywhere on your system—including on the hard drive you’ll be using for your clone. If Spotlight is active while cloning, your machine will also have to work hard while cloning—all those newly-created files will be added to Spotlight’s index. Another downside to leaving Spotlight active on your clone drive is that you’ll get double matches for anything you then search for—one match on your Mac, and another on your clone drive.
While some of these apps may block Spotlight on their own, I always do it myself, just to be sure the drive has been removed from Spotlight. To disable Spotlight, first connect the drive onto which you’ll clone your Mac’s hard drive. Assuming it’s already been formatted and is ready to go, it will mount in the Finder. Then open up the Spotlight System Preferences panel. Click the Privacy tab, then click the plus sign, and select your to-be-cloned volume in the dialog that appears.
I’m not sure there’s any speed to be gained by disabling Spotlight prior to cloning, but your CPU won’t have to work as hard while cloning, and you won’t get double matches when you finish. Speaking of finished, you might want to insure that the drive still appears on the Privacy tab after cloning—I’ve seen reports that sometimes cloned drives mysteriously vanish from the Privacy panel, though I haven’t seen that myself. Thanks to Mac OS X Hints reader Jules Hobbes for today’s tip.
Updated on Friday June 26th at 10:37am to correct an inaccuracy regarding which drive to disable Spotlight indexing on.