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10.5: One possible cause of huge Time Machine backups Apps
I have been using a Time Capsule for a substantial amount of time now, without major issue. But recently, I started to annoyed by huge, repeated hourly backups. For example, Time Machine would backup 1.6GB, although it seemed I hadn't done major file modifications since previous backup. And, more noticeably, a second, huge 1.6GB to 1.7GB backup would follow immediately, without even the hour delay between the two.

I started to scrutinize the Console log, with no hints to the cause of the repeated huge backups. Actually, I couldn't find any hint, because I filtered console logs using the search field with "backup" string. I accidently ran into the solution when I forgot filtering.

Although I am no console expert, I could read repeated references to the TechTool Protection tool, whch reminded me I had installed it recently. In the TechTool Protection System Preferences panel, I deactivated all protection functions, and my Time Capsule backups were back to reasonnable sizes.

[robg adds: It's the Directory Backup feature of TechTool Protection that causes these huge Time Machine backups. If you'd like to keep using that feature, you can add the folder that contains those backups (it's somewhere in your user's folder) to the list of Time Machine exclusions.]
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10.5: One possible cause of huge Time Machine backups | 9 comments | Create New Account
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10.5: One possible cause of huge Time Machine backups
Authored by: bjmorgan on Jul 16, '09 08:31:06AM

Bully for this discovery! I'd been having the same issues and had just assumed it was something I had done to create such a huge change.



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10.5: One possible cause of huge Time Machine backups
Authored by: seika7 on Jul 16, '09 10:28:44AM

Another possible cause is a slightly modified disk image such as the one used by Parallels for the Windows virtual hard drive.



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10.5: One possible cause of huge Time Machine backups
Authored by: CarlRJ on Jul 16, '09 10:51:22AM

(Huh, that was really neat -- I submitted roughly this same comment a couple minutes ago, with a link to the program, and was told "Spam detected" and my comment was unceremoniously thrown out with no chance to edit it. I'm kind of annoyed, as now I get to try to retype my comment from memory :-/. The preview certainly didn't tell me that it was considered spam.)

I've been pretty pleased with BackupLoupe (go google it yourself, apparently I'm not allowed to provide a link to it) for figuring out this sort of thing. At first I didn't quite get the point of the app, since I can poke around inside Time Machine backups just fine from the Terminal, but the genius of BackupLoupe is that it computes (and caches) the difference between each pair of backups (just the filenames and sizes involved), and then presents these in a view like a multi-column Finder window, with larger things color-coded, and sorted to the top of the list. This makes it trivially easy to drill down into any specific Time Machine backup to see what comprises the bulk of that backup.



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10.5: One possible cause of huge Time Machine backups
Authored by: BlaatMekker on Jul 16, '09 10:53:23AM
You can also use this hint (timedog) to find where the culprit is.

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10.5: One possible cause of huge Time Machine backups
Authored by: leisuremonkey on Jul 16, '09 11:29:44AM

Awesome! Thanks for the tip.

fyi... the folder Rob mentions is at ~/Library/Application Support/TechTool Protection



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10.5: One possible cause of huge Time Machine backups
Authored by: robg on Jul 21, '09 10:08:13AM

Thanks for the full path -- I was traveling and didn't have access to TTP on the Mac I had with me!

-rob.



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10.5: One possible cause of huge Time Machine backups
Authored by: iangoldby on Jul 16, '09 03:02:28PM

This is a different cause, but someone else might be reading here because some of their Time Machine backups take an excessively long time to complete, so I'll share it.

I've noticed that occasionally Time Machine will take an excessively long time to do a backup, and for most of the time the Time Machine control panel says that it is just preparing the backup. The amount of data to backup once it gets going is often rather small.

I think this happens when the Mac suffers a hard reset - i.e. it was shut down by a kernel panic or by holding down the power button after it became unresponsive. My theory is that Time Machine works by monitoring all changes to the filing system, so when it comes to do a backup it already knows what files have changed without having to compare the current files with the last backup. But if the Mac suffers a hard reset then it reckons it might have missed some changes. So it has to work out what files to backup the long way by comparing all files with the backup, and that takes a very long time.

So it's annoying but probably nothing to worry about and won't happen often.



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10.5: One possible cause of huge Time Machine backups
Authored by: palahala on Jul 16, '09 03:57:20PM

Your theory is almost correct. Your Mac keeps track of all changed directories (not all files), and Time Machine uses this information to only scan the directories for which it knows something changed. Indeed, if your Mac for any reason thinks that this information is no longer correct, then it will declare all the old information invalid. Time Machine then needs to compare your backup disk with your Mac's disk.

See also some very nice articles on Ars Technica and Earthling Soft.

Note that the logfile actually indicates this situation. See Time Machine Buddy to easily view that log.



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10.5: One possible cause of huge Time Machine backups
Authored by: maclick on Jul 20, '09 12:42:11PM

Thanks so much it has been making me crazy.



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