Bulletproof backups: When you absolutely can't lose any data

If you’re already backing up your Mac—perhaps by following the simple steps in “Backup Basics”—pat yourself on the back. Having any sort of backup is much better than having none, and your probability of recovering from data loss is dramatically increased. But for many people, a barebones backup strategy won’t cut it. If your livelihood depends on your data being available at all times, if you’re in the middle of a time-sensitive project, or if you’re just paranoid and want to make sure nothing has fallen through the cracks, you may want more of a guarantee.

How can you turn so-so backups into fantastic, bulletproof backups? Although everyone’s situation is a bit different, I have several recommendations that should vastly improve the quality and reliability of any backup plan.

Save old versions of files

One type of backup everyone should have is a versioned backup, which means your backup software continues to store older versions of your files when you change or delete them. OS X’s Time Machine does this automatically, as do Dropbox (), CrashPlan (), and the majority of modern backup programs. (OS X 10.7 Lion and later can automatically store multiple versions of your files, but this capability works only in apps that have been written to support it.)

Which software you use and the exact implementation details are less important than the outcome—if you (or a family member, coworker, or even a pet) inadvertently change or delete information in a crucial file, you want to be able to go back to an earlier state of that file before the mistake happened, even if that was weeks ago.

Some backup software saves new versions on a fixed schedule (for example, Time Machine runs once per hour), while other software lets you choose the backup frequency or watches files for changes and then backs them up immediately or after a user-defined interval (CrashPlan falls into this latter category). Given the choice, opt for more-frequent versioned backups.

Versioning is important, but by itself, it’s not enough. Your backup strategy also needs a few other key components.

Make a bootable copy of whole shebang

If you back up your entire disk with Time Machine, you can restore it later to its exact state from any of numerous times in the past. There’s just one problem: Restoring a whole disk using Time Machine takes a long, long time. (Depending on how much data you have, whether you used a local hard drive or a Time Capsule (), and several other variables, it could be anywhere from hours to days.) While that restoration is in progress, you can’t do anything else with your Mac. So, even if takes you just a half hour to replace a faulty disk, you realistically won’t get any more work done today.

That might not be a problem if you only use your Mac recreationally, but if you’re facing time pressures and don’t have another computer, it could turn into a crisis. So I always recommend a second type of backup: a bootable duplicate, which is a complete copy of your startup disk on an external hard drive, copied in such a way that you can start your Mac from the duplicate if necessary and get back to work almost instantly.

Need to start up fast after a crash? Carbon Copy Cloner lets you copy your startup disk to an external drive so that you can boot your Mac from the duplicate.

Many backup apps can create bootable duplicates, but Time Machine isn’t one of them. If you don’t already have a tool to create bootable duplicates, Bombich Software’s $40 Carbon Copy Cloner and Shirt Pocket Software’s $28 SuperDuper! are excellent choices. Be sure to update your duplicate at least once a week. If you need to start your Mac from the duplicate, make sure it’s plugged directly into your Mac, restart while holding the Option key, and select the backup drive.

Make backups for your backups

When it comes to backups, remember the adage “Don’t put all your eggs in one basket.” Several times I’ve had the gut-wrenching experience of looking for a crucial file in my backups only to find that the backup drive had itself gone bad, the online backup provider was down for maintenance, or something else made it impossible for me to get at my data.

With CrashPlan, you can configure multiple destinations for your backups. For example, you might set it up to put one copy on a local hard drive and another on CrashPlan's servers or a friend's Mac.

So I learned to keep multiple backups, on separate media. This could mean, for example, two different hard drives, or a hard drive and an online backup service, or a NAS (network attached storage) device plus Dropbox. But one way or another, I recommend having backups for your backups!

Keep some backups offsite

Make sure at least one of your backups is in a completely different location from your Mac at all times. After all, the same fire, earthquake, or hurricane that wipes out your Mac can wipe out your backup drives too. Also, if a thief breaks in and grabs your Mac, he’ll probably take that shiny backup drive as well.

If you use online backups in conjunction with a local hard drive, you can kill two birds (multiple backup media and offsite backups) with one stone. That’s also simpler than rotating disks from your home to a friend’s house or a safe deposit box. But whatever technique you use, be sure you have a backup somewhere safe from the dangers that could affect your Mac.

Walk through your restoration plan

The final—and perhaps most crucial—component of a heavy-duty backup system is a restoration plan. In other words, think through in advance precisely what you will do to restore your data, whether the problem is a single missing file or a dead hard disk. When you’ve just lost important data and are stressing over a deadline, you don’t want to have to figure out how to restore files—or worse, discover that your backup software wasn’t doing its job properly.

Don’t merely read the instructions for restoring your data; try it. In fact, performing test restores should be one of those tasks, like fire drills, that you perform every so often just to reinforce the steps. Adam Engst of TidBITS suggests putting a reminder on your calendar every Friday the 13th: “International Verify Your Backups Day.” Take a moment to make sure you can restore older versions of a few key files, and confirm that you can start your Mac from your bootable duplicate. That way, if and when a real problem occurs, you won’t have to panic; you’ll be secure in the knowledge that your data is safe and know exactly how to recover it.

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