Time Machine bug could cause data loss in backup process

Karen Haslam
11 December, 2012
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A bug in Time Machine is causing Apple’s backup solution to exclude certain volumes from the backup. This could lead to data loss, warns a report.

According to the report on MacPerformanceGuide, Time Machine can sometimes miss critical volumes from the back up without warning.

Lloyd Chambers wrote: “Time Machine auto-excluded these critical volumes and then posted a dialog saying there was nothing to backup – this time I was lucky. Usually, Boot remains (so no such warning is issued), but Master alone is excluded — my most critical files left unprotected.”

He explained that even after re-adding a volume from the list “it pops right back into the excluded list a short while later.”

Chambers claimed that he has been experiencing the issue in Mountain Lion since the beginning of December, and in Lion since autumn. He said he has bought it to Apple’s attention.

He admitted that he has a number of volumes that he excludes from Time Machine backup, because he backs them up separately. Normal users are unlikely to have multiple volumes for backup.

Chambers suggested that a possible cause of the bug could include the fact that he has around ten internal volumes. “Perhaps Time Machine simply has a bug in some kind of internal list.” Another suggestion: “Perhaps there is some side-effect of cloning a backup that confuses two volumes (they do all have different names). But TM identifies volumes by a unique ID, so this this does not make sense either.”

He also questioned whether the issue is the nature of the volume – whether it has a RAID-0 stripe. But, he concluded: “Time Machine ought to be looking at volumes, not drives, so I deem this idea unlikely also.”

Apple’s Time Machine is a backup utility that is built into OS X. It creates hourly backups of files, recording changes, rather than creating a clone. With Time Machine users can revert to the way their system was at any point in the past, either recovering a lost file or undoing a recent change – particularly useful in the case of a flawed update or an failed attempt to rebuild an Outlook database. Time Machine is also useful for migration of an old Mac to a new Mac.

One of the settings of Time Machine allows users to exclude certain file or folders from the back up, to save space for example. To add a file to the exclusion list go to Time Machine in System Preferences > Options > + > [select folder/file names].

Have you had any issues performing a back up using Time Machine? Let us know in the comments below.


2 people were compelled to have their say. We encourage you to do the same..

  1. Dylan says:

    I am currently going through an issue w/ Time Machine. I have an iMac which had one of the harddrives which Apple recently recalled and replaced for free. All was working just fine w/ my iMac ahead of the swap. Before bringing the computer in, I ensured that TimeMachine backed everything up. I then checked the data use on my harddrive through Finder and it read ~ 755Gb. When I got the iMac back with the new drive and restored the data, the drive then said I had 668Gb used.

    Apple tech support has not been able to give me a good explanation for how this happened and why the data fell away, or which if any data fell away. Their claims have been that TimeMachine backs up every single byte. If that were the case, then how did my data usage drop???

  2. E Carstens says:

    I purchased a new MacBook Pro Retina a couple of weeks ago. Migrated from a TimeMachine backup and everything went well.

    However, now, I am experiencing the “/Volumes/AirPort Disk-1/MyComputer.sparsebundle” is already in use.” problem. OS10.8.3 seems to be causing this error since the previous MacBook running OS10.6.8 TimeMachine worked flawlessly on the same TimeCapsule. Apple Support told me to restart TImeMachine. This worked for a while but then the error comes back. There must be a better solution than rebooting TimeCapsule each time the error occurs, no?

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