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10.5: Exclude local iDisk mirror disk from Time Machine Apps
Here's a tip, if you use .Mac with a locally-cached iDisk.

There are two problems with Time Machine and iDisk. First, while the iDisk .dmg file is backed up, you have no access to any folders within your iDisk through Time Machine. This is kind of unfortunate, as I keep my all my personal documents on an iDisk (locally cached at both ends) to keep my iMac and Macbook in sync.

Second, every time you make the slightest little change to your locally-cached iDisk, Time Machine has to copy the entire disk image again. The same would apply to disk images for virtual machines, for instance. In addition to making your hourly backup more time-consuming, this will quickly eat up free space on your backup disk. Since Time Machine for iDisk is already pretty useless, just exclude the local DMG of your iDisk from Time Machine backups. After all, all the files on it are already backed up on .Mac servers, and on your other computer.

To do this, open Time Machine's System Preferences panel, click the Options button, then click the plus sign to add a new excluded location. In the file dialog that appears, navigate to ~/Library » FileSync, and click the Exclude button. I'd also recommend excluding any other large disk images you might have -- you can just make manual backups of these. Otherwise, your Time Machine drive is going to fill up pretty fast.

Hopefully, a future update to Time Machine will have special provisions for these large, frequently-updated files, and possibly will provide an interface for iDisk backups. (One solution to the iDisk problem would be to not have the local cache of the iDisk be a disk image, but rather some hidden-away bundle.) In the meantime, save yourself a headache and exclude local iDisk images and other large files from Time Machine.
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10.5: Exclude local iDisk mirror disk from Time Machine | 7 comments | Create New Account
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10.5: Exclude local iDisk mirror disk from Time Machine
Authored by: filmsmith on Nov 08, '07 08:57:59AM

Under Leopard, if you turn off iDisk Syncing and then turn it back on, your local copy of your iDisk is recreated as a SparseBundle. The advantage to this is that when a file is deleted from a SparseBundle, the system is able to immediately reduce the file size of the image because it's actually a series of 8 meg files segmented to make up the entire image. (Right click on a SparseBundle and choose "Show Package Contents" and in the folder Bands will be these files)

Now, my hunch is that Time Machine works with SparseBundles to back up only those tiny bits of the image that have change and not the whole thing, but I can't be 100% without knowing exactly what it is Time Machine is archiving.

I've tried forcing Time Machine right after modifying only my iDisk and the size of whatever Time Machine is moving is significantly smaller than my entire iDisk, though I don't want to speak with authority without being certain.

Anyone else want to weigh in on this?

-dennis



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10.5: Exclude local iDisk mirror disk from Time Machine
Authored by: imcquill on Nov 08, '07 11:08:44AM

You are correct. It is easy to check. Right click time machine and back up now. Then go to your time machine volume, check the amount of space taken up by used space. Then, make a tiny change on the idisk.. say add a byte to some text file. Then backup again with time machine. My idisk has about 1GB of space used but after this test, the time machine volume is only using about 1MB of extra space from the first backup.. it does not backup the entire volume, but only the *bands* within the package of the sparsebundle which have changed.



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10.5: Exclude local iDisk mirror disk from Time Machine
Authored by: yDNA on Nov 08, '07 12:22:11PM

Now that (iDisk SparseBundle feature) is seriously cool. Thanks for the tip!



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10.5: Exclude local iDisk mirror disk from Time Machine
Authored by: barrerboy on Jul 28, '10 09:07:21AM

It seems to me a considerable amount of tech knowledge is needed to manage iDisk. My geekability is low, I just want to be a user. I am going back to dropbox which is much friendlier. If only I could figure out how to get rid of 'Previous local idisk' and all the other associated space consuming junk which is littering my Macbook.



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10.5: Exclude local iDisk mirror disk from Time Machine
Authored by: ferret-slayer on Nov 08, '07 10:01:31AM
Hopefully, a future update to Time Machine will have special provisions for these large, frequently-updated files....
That would be ZFS. A ZFS "snapshot" would only include those disk-sectors that have changed since the last snapshot.
TM currently uses HFS+, and has to copy the entire file if a single byte changes.

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10.5: Exclude local iDisk mirror disk from Time Machine
Authored by: imcquill on Nov 08, '07 11:12:49AM

It is a package (which means it is a folder) and not a single file. It is definitely only backing up bands (which are at most 8MB) that have changed within the sparsebundle. Leaving it included has the advantage that if you want to recover the contents of your idisk on a previous day, you could.



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10.5: Exclude local iDisk mirror disk from Time Machine
Authored by: FOOOD on Nov 08, '07 01:27:59PM

Good tip thanks.
It might also be a good idea to delete all versions of the FileSync folder from Time Machine.

(Go to your Library folder, activate Time Machine. Select the FileSync folder, click on the action button in the toolbar & select 'Delete all Backups of 'FileSync').



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