Blog Post

Syncing Does not a Backup Make

Syncing data to the Internet (“the cloud”) is all the rage these days and with the coming of the iPad, we’ll surely see more of it. Whether you are using MobileMe, Dropbox, or any one of the variety of other syncing programs, you may be one of the increasing number of people using these services to backup their data.

The problem, though, is that syncing is not backing up.

Syncing’s main focus is making sure your data is accessible and identical at multiple locations. If you have a disaster at one of these locations, a syncing service will make sure you still have access to your stuff. That’s handy and is seen by people as a way of backing up. Lose your iPhone and your contacts are accessible via the web. Sync to Dropbox and if your MacBook hard drive dies, you can access your synced files via the web or another computer.

Unfortunately, syncing operates under the age-old computer principle of Garbage In Garbage Out. When syncing is working properly, a change made on one device is propagated to the web and to all other devices. If that change was unintended, the service might have a previous revision, but don’t count on it. A problem with data on one device is copied to all other devices in your sync scheme.

When it’s not working properly, stand back because things get ugly. I was a recent victim of this. I’ll be polite and won’t mention the name of the service, but it wasn’t a “sweet” experience. Somehow this company’s database was corrupt for my account and instead of syncing changes I made on my Mac to my PC, the server decided I had deleted a critical folder. I literally watched as the software started deleting folders from my Mac without warning or confirmation. I immediately unplugged my Internet connection to minimize the damage. While only the fates of the cloud know what really happened, the post-mortem analysis I had with their engineers indicated my PC’s sync database somehow “thought” I no longer had a folder on my hard drive and then told the cloud to delete it from other computers. Blame it on a PC to mess up a Mac. Of course, their server didn’t have a backup. A two-fisted punch right to the gut.

These same concerns also hold true for your calendars and contacts from MobileMe. Even though you sync them to the cloud, you should still perform a local backup of your Address Book and iCal. Don’t be lulled by the siren of the cloud assuring you that your data is safe. The cloud is a jealous mistress who can swipe data right from your hard drive. Being old school, I don’t fully trust syncing or the cloud and so I fully backup my hard drive via Time Machine and dedicated online backup services. While my sour experience was annoying, I was able to quickly recover.

Others have not been so lucky. Account and database corruption are a fact of computing and because syncing doesn’t only copy data, but remove it, it’s not a backup solution. A true backup solution cannot remove data from your drive, only copy it. Whenever I read backup software reviews, commenters ask why synchronization services aren’t mentioned. Now you know why.

Don’t rely on services like MobileMe and Dropbox as a backup. Your data will thank you.

28 Responses to “Syncing Does not a Backup Make”

  1. Good article Dave, and a wakeup call for people like myself, that were lulled into a false sense of security with syncing services!

    I agree that your solution of a local backup using Time Machine, and offsite backup online is the best way to go.

    I’ve been using a Time Machine for my local backup for the last 10 months, but I knew that a local backup was only half of a disaster recovery solution — because in my worst case scenario there wouldn’t be any local backup to recover from!

    3 weeks ago, after reading a couple of TheAppleBlog articles about Backblaze backup (, I decided to sign up for a free trial. A simple online backup solution with unlimited storage, for just $5 a month, sounded too good to be true. But it was indeed true, and before my 15-day trial had ended I’d signed up on 2-year plan for only $95.

    This week I implemented a 3rd backup solution for my most important data — all my 1Password logins. I created an Automator workflow to find and archive my 1Password files (in 1Password help, there are 3 files that they recommend you backup) to my iDisk, and an iCal event to schedule a daily backup (there’s an article about scheduling automator workflows here:

    Now I feel much more secure about my data, because I have multiple backups in multiple locations ;)

  2. Sandman

    Great post. I personally use a combination of Sugarsync, JungleDisk (to Rackspace Cloudfiles), Arq (to Amazon S3), Backblaze, Time Machine and Chronosync myself :D

    By the way, what is a good way to automate exports and backups from OS X’s Address Book and iCal?

  3. CrashPlan provides backup options like online backup and remote backup to your own computers that can complement Time Machine’s backup or replace it altogether.

    Both provide version history, the ability to fetch a version of a file or files from a previous point in time.

    This is a key difference between backup and synchronization, which is emphasized here. In other words, synchronization doesn’t protect your from mistakes, whereas backup does.

  4. SMorley

    I have just cancelled my SugarSync account (despite paying up until November 2010) because of slow, dropped connections and an annoying habit of duplicating data for no apparent reason. I didn’t loose an data, but I guess it was only a matter of time. Dropbox has proved to be a far more reliable service sync’ing on a small scale, with Chronosync over LAN for larger scale (music, photos), and Crashplan and Time Machine to take care of backups. Can’t be too careful!

  5. I have a couple of layers of backup. Locally on my Mac I have a 1TB drive attached, this is used for TimeMachine, to backup my Mac and everything useful on it, and because of OS X unix goodness, rsync scripts copy critial data folders from my Linux file server.
    Then Once a month I duplicate this to another 1TB drive on a sunday night, then take that drive to work and keep it there. The problem with backing up in the cloud for us here in NZ, is the cost of data. I only get 20GB a month, so backing up 1TB of data!! Hahahahahahahahah. Let alone restoring it would take forever.

  6. mikesel

    I completely agree with the article. I am looking forward to finally getting hold of a ‘Time-Machine’ until then I use several different backup methods depending on what files I am backing up.

    Unlike some, I don’t like having ‘all my eggs in one basket’ I even use Microsoft’s Live Mesh as a backup. Which as of yet I have not seen mentioned. I like mesh, as it provides a convenient working solution over several PC’s whilst also providing a constant backup solution.

    I have MobileMe, but I don’t use the online storage currently. I will now be weary of where I keep my keychain’s.


  7. I agree with the article completely, there is a big difference between syncs and backups. While the poster has issues with the software package, it should also be noted that nothing actually needs to ‘go wrong’ with the program at all for you to lose you files. Human error can even play. Say you accidental hit ‘delete’ on your folder, that delete will be propagated to all your computers.

    However, as others have said, many of the cloud providers do create backups or take snapshots. There is always going to be the issue of what to backup and when. With my photoalbum though, I would never trust Dropbox or any third party application to backup my files properly, the contents are just too critical.

    Another issue, especially with services like Dropbox that allow multiple people to work on the same file on different machines. There will always be a clear winner and data could be lost more easily than some think. There is no easy software solution around it, and merging files edited in two locations is cumbersome at best if possible at all. If you’re using Dropbox for personal use, there is really no problem because there can only be one of you at a computer at a time. Just be careful when sharing documents with classmates or colleagues.

    As far as backups go, A you should always have one more copy than you current have backed up. ;)

  8. I use Sugarsync, which offers file versioning – except when it doesn’t, like not for example of my Scrivener files (word processor).

    Anyway, that’s why every knowledgeable security guy recommends to use at least two independent backup solutions.

    In our small office for example we use additionally Jungle Disk (Amazon S3 cloud storage) and Time Machine/Time capsule…

    • Redundancy: the watchword of the IT professional .

      I wondered why grandpa wore a belt and suspenders: now I know.

      Redundancy: the watchword of the IT professional. I already said that and I’m being redundant on purpose

  9. I’ve had this problem with Dropbox on 3 separate occassions – each time they did the restore – but i had to notice that the files were gone. Even with their engineers restoring the files – it’s hard to feel comfortable with random deletes…

  10. I completely agree with the issue of syncing/Backup. One question though: Is time-machine enough to create incremental backups of your mobileme data? It seems like the necessary files are backed up on the external HD.

    • That’s what I do personally. I have Time Machine and an online backup service backup my data. When my sync database gets corrupt I’ll notice that contacts are missing, I’ll restore a backup of my Address Book data from Time Machine or online, and then reset my sync services (topic for another article).

      As long as you use another backup system to backup your synced data you should be fine. Using it as your only method and relying on that method, that’s what concerns me.

    • GlennAC

      @BROR “Is time-machine enough to create incremental backups of your mobileme data?”

      Yes, but only if 2 things are true.

      1) Are you syncing your iDisk to your Mac’s Desktop? If so, then there is a sparsebundle disk image created at the following location ~/Library/FileSync/###########e/BROR_iDisk.sparsebundle.

      2) You are not excluding the above location in your Time Machine Preferences. If not, then your iDisk is indeed being backed up by Time Machine. In the event of disaster, you can Restore the above sparsebundle and retrieve your missing files.

  11. well that’s a nice article and very informative…I do regular backups but always wondered what would happen if something went wrong with cloud syncing…

    thanks for the info

  12. jedcred

    This is true…except when it’s not. In the case of Dropbox, which allows you to recover several past revisions of files as well as recovering deleted files, this isn’t quite the problem you make it out to be.

    MobileMe may not do this, but never having used it personally, I cannot say.

    • I agree :-)

      It’s true that Dropbox makes backups and is protected those items…except when it’s not. Same with hard drives, the store data…excpet when they don’t

      If it’s sync database gets corrupt, the computer’s date is off or you don’t notice the file is gone, you are out of luck. Many stories out there from multiple sync service vendors. SugarSync claims the same backup service…except when it doesn’t

      When a backup goes bad, you don’t destroy data When a sync goes bad, you do.

      Read the Dropbox terms of service. They clearly state you should backup your own data