I've got a Synology NAS here and a few months ago I sadly got the message, something like

Time Machine backup is corrupt and therefor has to start a new backup.

However, as my NAS is starting to get more and more filled, I'm seeking to kill some data. I found this old backup which is about 650GB of size.

And my only question is: Can it be of any use or should I just remove it completely?

If you ask "But by starting a new backup, the old one gets deleted. Why do you still have it?" That's because it ended up in the Trash, instead of permanently deleted.

  • Is that the size of an entire backups.backupdb folder, or a subfolder therein? – the eels have eyes Jul 2 '15 at 2:25
  • It's the size of a complete backup. With all iterations of the past year. Note that this is a network (TimeMachine) backup, not a local drive. Therefor there are no directly accessible files, only 80.000 parts, each 8MB. – Sander Schaeffer Jul 2 '15 at 9:25
  • If you double click on it, does it eventually show up in Finder's sidebar, or do you get an error? – the eels have eyes Jul 3 '15 at 1:41
  • After I double click on it- and waited for about 30 minutes, I got the message, somewhat like "The TimeMachine Backup 'Macbook.sparsebundle' could not be activated. I could right click it and view it's contents, which includes the 'bands' folder, which includes 80.000 8MB files.. – Sander Schaeffer Jul 3 '15 at 10:27

The nature of Time Machine is such that it isn't an archival backup, as files deleted from the source drive will eventually disappear from the Time Machine backup set.1 If you have no other backup however, it might come in handy.

If the sparsebundle can be repaired, you'd be able to extract files from it. Following the instructions in the first green box of http://pondini.org/TM/A5b.html might let you access the backup set.

If you do gain access to it, you can use the Time Machine interface2 to remove all backups of folders you don't care about, but it might be tricky to cause the sparsebundle to take up less disk space.3

1 See the text starting with "Time Machine keeps" in https://support.apple.com/HT201250
2 "Remove a backed-up item from your backup disk" - https://support.apple.com/kb/PH11241
3 "Changing the size {…} of a sparse bundle" - http://pondini.org/TM/A8.html

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Well. You reached to the point where all these so called NASes already not work. During development I did a big data transfers to the nas via smb.

  1. For 1gb or 10gb it works, but when we speak about 100gb or 10tb smb implementation in OS X will not gonna work. It may be bugs in smb implementation in OS X or smb implementation in your NAS. Or in both.

  2. Another problem with smb is the internal cache. If you experience sudden mount point disconnect - your backup may not survive.

  3. Another problem is you may not even notice that, before you try to extract the data.

If you would like to use TimeMachine connect the drive directly to the computer. Or use Apple Time Capsule with original afp implementation. If you receive the error message, obviously some important(file table in dmg) data was corrupted. If your backup was encrypted imagine the consequences. Strictly saying if you do not check the backup(complete restore) you may think that your backup does not even exist.

Personally I recommend to use sftp if you would like to backup to remote disk. And you may try some third party software like immortal files or arc backup.

And finally if your data is not located in three different physical location it does not simply exist. It is only the matter of time when is will disappear in the dust.

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