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Trashed a time machine folder; is my whole backup likely damaged?

I dragged what was then the latest backup folder to the trash and thought nothing more of it for a week or so.


Then I went to empty the trash, and as the number of items to be deleted went into the 5 figures, I realized that I might have a big problem.


I've tried dragging the folder back into the Time Machine folder (Backups.backupdb), but no dice; first it said that my admin password would be needed, and then it said that it couldn't do it.


I've now dragged the folder back onto my big external drive where Backups.backupdb lives, into a random work folder. The finder progress window tells me that it is copying nearly 350,000 items totaling 168.49 gigs, and that the copy operation will take 9 hours or so. (Edit: After 40 minutes or so it's now predicting about 5 hours; I'm aware that this kind of prediction is only rough approximation until near the end of the process.)

This information suggest to me that I'm in a pickle. My incremental backups typically have a few tens of megs, sometimes a bit more. Even allowing for the fact that I know that Time Machine stores files in a specialized non-intuitive way, it seems deeply weird that one incremental backup folder has so many files. My Time Machine is set to back up only my ~ 500 gig internal drive, which holds about 300 gigs worth of files with about 180 gigs available. So this one "incremental" folder is more than half the size of the whole drive being backed up.


I'm hoping that when the copy process is over that the folder will no longer be in my trash folder, because I've read that emptying the trash may now be a problem, but I realize that this is unlikely. (Fortunately the external drive has terabytes to spare, so I don't have to worry about running out of space.)


Anyhow, my big concern is whether I have now hosed my whole set of Time Machine backups, which goes back a few years. Is there any way to check its integrity?


It would be a drag if I had to delete the whole thing and start over, because I would lose the ability to recover now-deleted files, but I'm much more concerned about the integrity of the whole backup in case I need to restore the entire drive. (In fact, I'm way overdue to abandon Snow Leopard; still looking for replacements for Now Contacts and Eudora. /off topic).


Grateful for any suggestions.

iMac, Mac OS X (10.6.8)

Posted on May 2, 2016 5:31 PM

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1 reply

May 2, 2016 11:46 PM in response to tttny

First off, you likely haven't trashed your entire backup.


Even though any given incremental backup is only a few megabytes/gigabytes, the way they are represented in the Finder is as a snapshot of how your disk looked at that time. It does this via a combination of pseudo-magic that just links older versions of the file into the current snapshot.


The end result is that if you copy any of the incremental folders, you get a full disks-worth of content even though only a small amount of data is unique to that snapshot.


As for the deletion process, this also won't delete older copies of your data - the only thing you'll lose (assuming the deletion process runs to completion) are versions of files that were new/changed in that snapshot and in the subsequent one, which is likely a small number of files.


As a more general lesson, though, don't futz about with Time Machine backups 🙂

Trashed a time machine folder; is my whole backup likely damaged?

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