Mac Backups, part 3: Whole disk duplication

It's not a matter of if your hard drive is going to fail. It's a matter of when.
--Zen proverb

In Part One of this discussion of backups we talked about what you might want to back up and how to organize it, and in Part Two, we outlined relatively painless methods of backing your critical data up to another disk. In Part Three, we'll talk about duplicating your entire hard drive, and how to go about it.

Despite my admittedly overzealous approach to critical data backup, there are times when I want a reasonably fresh copy of my entire hard drive -- OS, Applications, settings, data, everything -- all nicely lined up the way I like it. But why go to the trouble? I've been doing daily backups of all my critical data, and I have installation disks for the operating system and all of my application programs -- why do the extra work?

Very simply put, you will have a hard drive failure at some point. Count on it. And a whole-disk backup can be a big time-saver when that happens.

Let's go back to when you first bought your system: it arrived with an operating system already installed, and whatever core programs (iPhoto, iTunes, etc.) that came with it. But of course, between the time the machine left the factory and when it arrived on your desk, a couple of OS updates and maybe a security patch were issued, so they had to be downloaded and installed...and those updates are getting bigger all the time. The last OS update I downloaded was over 700 megabytes; a big download no matter how fast your Internet connection is.

You've also invested a fair amount of time installing and configuring application programs, utility programs, printer and scanner drivers, and stuff like that. And time is money. That's where products like Carbon Copy Cloner or SuperDuper (catch the play on words?) come in. Either of them has the ability to duplicate an entire drive, with all your OS updates and programs intact. Your drive can be duplicated to another drive, or all poured into a single file called a disk image (called a DMG, not to be confused with OMG!).

The advantage of taking the first route -- duplicating to another drive -- is that it gives you the ability, in the event of a hard drive failure, to simply restart the machine from your backup drive and go back to work with a minimum of lost time. If you've also been using something like Chronosync to back up your critical data on a regular basis, you have a setup that cuts your losses almost completely -- or at least down to losing only that work you've done since the last backup.

I do a whole disk backup more-or-less annually. Why so infrequently? Because it takes a lot of time, depending on how large your primary drive is and how fast your machine is. My last one took something like six hours. But hey -- once my disk has everything installed and updated, there ain't that much that gets added through the year. If I happen to do a big upgrade -- say from OS X 10.5 to 10.6 -- then I do another whole-disk backup.

The process is pretty straightforward: as with Chronosync, you specify a source disk (the disk to be copied), a destination disk (the disk you're going to copy it to, and hit "Go!" (Hint: configure your backup and start it just before you leave the office for the day. Let it run overnight. Makes things fairly painless.)

The result is a total mirror image of your hard drive; a functional twin of your primary drive. If your primary drive crashes, you simply reboot from your backup and continue working (while you send someone to get a replacement for the drive that just crashed, muy pronto).

The important thing to remember here is that you need to have an empty -- as in totally blank -- hard drive to copy to, because your destination disk will be completely erased before your primary drive's contents are copied to it.

When the copying is finished, you're done. Don't do anything else with your new backup except let it sit there -- unless your primary drive crashes, of course.

The ability of SuperDuper and Carbon Copy Cloner to create a single file containing all of your primary hard drive can be useful sometimes, too. I have one client who does a single-file clone of her hard drive every couple of months to one of those little external hard drives that looks like a deck of cards, and then puts the backup drive in her safe-deposit box. This gives her an offsite backup, in case of fire, flood, theft, vandalism, or ghosts in the machine. With pocket-sized external drives under $100, it's fairly cheap insurance -- remember, a computer or hard drive can be replaced. Your time and critical data can't.

The DMG file that's created will be roughly the same size as the sum total of the contents of the drive being imaged, so be warned that files get pretty big. Also, you'll have to unpack this to another hard drive to be able to boot from it. But having said all that, I find it kind of comforting to have an image around somewhere, just in case. I mean, it don't cost me nothin'...

As always, if you have questions feel free to send me an email.

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