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Using Time Machine on unsupported volumes
Authored by: Supp0rtLinux on Apr 17, '14 11:24:34AM

This is handy... you're basically making a filesystem within a filesystem. If you google around a bit, there's way of making that sparse bundle file dynamic in size and encrypted too. I do this on an external drive. The entire drive is HFS, but within I have a dynamically expanding and encrypted sparse bundle on it. Works out pretty well as I don't have to "reserve" a certain amount of the space of the source drive... allows me to use the rest of the drive as I see fit. In the old days, I had a 1Tb drive setup like this with 500Gb for general storage and 500Gb as my encrypted sparse image file. But the sparse image was only 200Gb full while the other 500Gb partition was almost full. That's when I redid it to have the sparse bundle grow dynamically. The basic idea is laid out here: http://www.cnet.com/news/how-to-set-up-a-dynamically-resizing-disk-image I think this would work well for your idea as well. Just bear in mind that not all filesystems will support this. exFat will. So will HFS. NTFS will work too if you pay for the options to get write support for NTFS in OS X. But regular FAT won't due to max length for filenames, etc. Just be aware of the limitations of the underlying unsupported filesystem.



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Using Time Machine on unsupported volumes
Authored by: Strod on Apr 18, '14 02:32:32PM

Another limitation of FAT32 that people may want to take into consideration if they want to use the hint is this:

While under some circumstances a FAT32 volume can be up to 2 TB (IIRC), a Disk Image created on it is limited to at most ~ 500 GB.

The reason is this: Files in FAT32 can be at most 4GB, so the only way to get a Disk Image greater than that is to make is a Sparse Bundle. BUT:

Sparse Bundles store the contents in "bands", that is, files that are at most 8 MB (that's 8 x 1024^2 bytes). So far, so good. But all the bands are saved in the same subdirectory, and AFAIK FAT32 can hold at most 65,535 files in a single directory.

65,535 files * 8 MB per file = 512 GB (where 1 GB = 1024^3 bytes). So your internal filesystem can hold less than that at most.



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Using Time Machine on unsupported volumes
Authored by: davidallie on Apr 22, '14 07:04:26AM

Thanks for the info and link, Supp0rtLinux. The CNET article was helpful. As I read it, I wondered about the differences between sparse disk image and sparse bundle disk image, so did a search and came across a really good article by Mike Bombich (of Carbon Copy Cloner) that describes the differences between the two types.

Better yet, Mike provides an applet that will compress sparse bundle disk images. Check it out here: http://help.bombich.com/kb/dmg-and-remote/backing-up-to-a-disk-image

Edited on Apr 22, '14 07:04:55AM by davidallie



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