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Yann Bizeul Author

Level 4

1,354 points

Do not trust your Time Machine backups

I had a very unpleasant surprise yesterday : I found out the hard way that I could not trust my Time Machine backup...

Once booted in recvoery mode to select "Restore TimeMachine backup", the process starts and seem to happily finish a few hours later (surprisingly, it finished when actuall 3 hours of restoration are indicated). No error message, just a confident statement that backup is restored and the computer will reboot in 10 seconds.

Thing is, well, the computer wouldn't boot... I just got a black screen right after the Apple logo, no mouse pointer, just a plain black (backlighted) screen on my MacBook Pro.

I know my way in the system, I'm pretty technical, so I decided to not give up, after a few hours playing around with recovery boot, terminal sessions and log file reading, it appeared that a lot of files were missing, especially system files.

As an example : most content in /usr/share/shadbox, but also ll /System/Library/CoreServices/logind and other files.

After copying these files either from a very old Time Machine backup from end January or from another computer, I finally manage to boot the system.

Lots of applications ar not usable because of missing contents (AppStore, Disk Utility, etc, etc)...

This is totally unacceptable, I work in the computer storage industry, our customers would burn us down to the ground if they could not rely on their storage.

What's worse ? Looks like there is no way to check a backup. Apple provides a "Verify Backup" option in the Time Machine menu, but it is only valid for network backup, not local disks.

Thing is, I was happily looking at my backups every hours, running without errors, througout many many days, only to realize when I need it that it is corrupted.

What do people do when they need reliable backup, except for paying big buck to company who actually care ?

MacBook Pro with Retina display, OS X Mavericks (10.9.3)

Posted on Jun 5, 2014 6:44 AM

33 replies

benwiggy

Level 4

1,479 points

Jun 5, 2014 12:29 PM in response to MichelPM

I think that the statements "TM does not work" and "TM does work" are both over-simplications.

Personally, TM has never failed me in the 7 years I've been calling on it. But that doesn't mean that it is flawless. And you can say the same for many other similar products. I've had nightmares with Retrospect tape backups in mission-critical commercial environments.

**** happens -- even to backup software. Backup software prepares you against your hard drive failing, but for ultimate piece of mind, you need to prepare against your backup failing, too.

Yann Bizeul Author

Level 4

1,354 points

Jun 5, 2014 12:35 PM in response to benwiggy

IIRC, all backup software with self esteem will have an option to check backup. Read, compare, done.

Retrospect had that option, I pretty sire most tape backup software does. As I said, I can accept a filesystem silently fails and prevents you to access some data, and it is my responsability to run a check on my backup from time to time. But with TM, I can't even do that because there is no tool.

LD150

Level 10

91,531 points

Jun 5, 2014 1:05 PM in response to MichelPM

With a lifetime in Windows and 2 years on Macs I would say Time Machine is a true gem of a differentiator and Windows has nothing to match it. TM has never failed me and I have fully restored twice and recovered dozens of files. Secondary backups for my media and documents of course, but TM is superb.

Yann Bizeul Author

Level 4

1,354 points

Jun 5, 2014 1:14 PM in response to LD150

I never had issues with TM before, did multiple OS restored when I switched machines, restored files occasionaly.

Point is, that's a difference between a "useful" software and a "critical" software.

Backup is critical. And we are not talking about failing backup, we are talking about backups missing a lot of files *silently* with no way to verify. But I repeat myself, I guess I made my point already :-)

Jun 5, 2014 1:24 PM in response to Yann Bizeul

So a quick Google search revealed the presence of the "tmutil" tool in the Terminal. A quick look through the man pages reveals a compare function.

Something like "tmutil compare" would default to verifying the first time machine snapshot with your current filesystem.

Edit: actually I just read the comments above. Nevermind.

tbirdvet

Level 6

14,753 points

Jun 5, 2014 4:38 PM in response to Yann Bizeul

I have used TM for several years and had to restore and migrate from old Mac to new several times and no issues. However, like any backup hardware/software I never trust it alone. That's why I also use CCC weekly to clone my drive.

MichelPM

Level 10

81,306 points

Jun 5, 2014 5:16 PM in response to LD150

Get back to me when you start getting failed system restores and even when you start experiencing failures with incremental data restores.

Then we will have a conversation.

If your data and files are really very important to you and you never, EVER want to lose that data, archive to CD/DVD disks for a more permanent archive of your really important data and DO NOT RELY OR JUST RELY ON OS X TIME MACHINE, period.

All it takes is one time where Time Machine fails to do a complete system restore and with no other redundant backups or use of another Backup method, you are scrawed.

Data cloning is far, far more consistent and reliabe than the method/s Time Machine employs.

LD150

Level 10

91,531 points

Jun 6, 2014 1:12 AM in response to MichelPM

Rather a polarized opinion but of some value. If i trusted TM s as sole backup I might agree, but as I said other direct copies of valuable data are also taken but so far never needed. Meanwhile the ability to retrieve different versions of the same document from over a year ago, whilst they can never be guaranteed, is still handy when they are there. Clones tend to be the most recent, and do not contain deleted files (unless you clone your Trash?). Also what about the file you created since your last clone, like two hours ago?

You got your 10 points, be happy.

benwiggy

Level 4

1,479 points

Jun 5, 2014 7:11 AM in response to Yann Bizeul

By the way, there IS a Verify Backup option for local disks. Hold down alt while clicking the TM menulet, and it appears there.

Yann Bizeul Author

Level 4

1,354 points

Jun 5, 2014 7:12 AM in response to benwiggy

It is grayed out for local backups, it only works with remote

Linc Davis

Level 10

209,673 points

Jun 5, 2014 8:50 AM in response to Yann Bizeul

To clarify, you had an apparent Time Machine failure while running a pre-release version of OS X? If that's what happened, why are you reporting it here in violation of the NDA?