Time Machine - Frequently Asked Questions

27. Can I have "dual" backups?   Or back up my Backups?

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I've learned over the years (mostly the hard way, of course),  never to trust my backups to a single app or piece of hardware:  ALL  hardware fails, sooner or later, and  NO backup app is perfect.  And, anyone who hasn't erased the wrong drive yet probably will, one of these days.

Clearly, there's a need for multiple backups.  The questions are, how? and how many?

How many? is a question only you can answer.    Some or most of your data may be absolutely irreplaceable -- your children's pictures, wedding videos, etc.  Other stuff, maybe not so much.  For most of us, it's all in one place, so we need a single strategy -- one, two, or more backups. But if you have original data on separate Macs and/or external drives, you may want more backups of one than others.

How?  There are several ways to have multiple backups, detailed below:

  1. Back-up your backups

  2. Dual Time Machine backups

  3. Use a different backup app

  4. Off-Site backups

Off-Site backups:

If all your backups are in the same physical location, you’re not protected against fire, flood, theft, direct lightning strike on your power lines, and the like.  There are two basic methods:

  1. Internet backups

  2. There are a number of services that allow backups via the internet, but in most cases, it just takes far too long to back up or restore an entire Mac that way.   Most internet connections have about one-tenth the upload speed as their download speeds -- it can take days to do a full backup of a large system.  Some of those services ship you a portable external HD for you to do the first backup;  when you ship it back, they load it onto their servers!  Even with faster download speeds, it can take many hours, perhaps days, to do a full restore.

  3. Also consider the security of backups on some server, somewhere.  Are those servers backed-up?  What happens to your data if you change email addresses and don't realize you didn't get notices for the renewal fee, or if the company goes bankrupt?

  4. It can be useful, however, to use those or other services to back up limited amounts of critical data to an internet server.  DropBox and SugarSync are a couple of popular ones.



  1. Use a Portable external HD

  2. Perhaps the safest, most reliable, way to keep off-site backups is with a portable external hard drive, with Time Machine or one of the apps in the green box above, and take it to your safe deposit box, workplace, relative’s house, or other secure location regularly. 

  3. Even better is a pair of them.  Use one for a week or so, then take it off-site and swap with the other, so one is always in a separate place from your Mac and local backups.                                 

  4. In some cases, just copying things to CDs/DVDs and taking them off-site is sufficient.  Just be sure to re-copy them every year or two, as they don’t last forever.

Backing-up your backups:

It’s generally not a good idea to copy or back-up your backups.  If there’s a problem on your primary backups, it will be copied to (and perhaps magnified on) the secondary ones. 

If your backups are on a Time Capsule, you can "archive" them to a USB drive connected to the Time Capsule.  See How do I back-up my Time Capsule and/or Air Disk?   As you’ll see, there are some downsides, however, so that's probably not a good strategy.

"Dual" Time Machine backups:

Some folks do, or want to, keep two separate sets of Time Machine backups.  That can be done, but may not be the best strategy for redundant backups -- if there's a problem with Time Machine, your backups may not be as reliable as you think.  It's a bit safer to use Time Machine with one destination, and a different backup app with the other.  See Use a different backup app below.

Effective with Mountain Lion 10.8.x,  Time Machine can automatically back up to two or more separate destinations, in "rotation."  Each backup is completely separate and independent from all others.  Backups are run hourly, but each available drive is backed-up to in turn.  See FAQ #34 for details, instructions, and considerations.  

On Lion 10.7.x and earlier, Time Machine can’t do that automatically, but you can do it manually, by telling it each time you want to switch, via Time Machine Preferences > Select Disk.  That’s easy to do, but since you can’t automate it, not very handy to do often.  

If you do that, note that each set of backups is completely separate and independent.  When you "switch" destinations, the next backup will be of all the additions and changes since the last backup to that particular destination.  If it's been a while (or there have been lots of changes) since the last backup to that destination, the backup may take considerably longer than usual.

Use a different backup app:

Your best, safest, bet is to use a different backup app, such as CarbonCopyCloner or SuperDuper!, for your "secondary" backups.  That way, if there's a problem with either app or destination, you'll still have the other one.  

CarbonCopyCloner is usually $40 U.S. with a 30-day free trial;  SuperDuper! has a free version, but you need the paid one (about $30 U.S.) to do updates instead of full replacements, or scheduling.  These make "bootable clones," rather different from Time Machine.  See Time Machine vs. Clones and Archives for an overview of the differences.

Some other options are: Data Backup, Deja Vu, Synk Pro, ChronoSync, and Tri-Backup

Backups are one area where Paranoia is Prudent!

Backups aren't a "one size fits all" sort of thing -- what's good in one circumstance may be inadequate for some, or overkill for still others.

You'll have to consider the importance of your data, your budget, your setup (a single Mac vs. multiple Macs and/or data spread over several drives), and your habits, to figure out a good strategy for you.

And, what works well now may need to be re-examined when your circumstances change.