I'd like to recreate a feature of Mac OS X called sparse bundles (disk images made out of smaller files, making them easy to backup after a small change). For that I'm looking for a way to 'virtually' create a single file made by concatenation of smaller ones (big.file shouldn't use all this space, just link to .files):
4096 0.file 4096 1.file 4096 2.file 4096 3.file 4096 4.file 20480 big.file
so that I'd be able to mount big.file using loop device, format as btrfs and upon writing to this disk, data should be written only to certain .files, allowing me to backup easily.
Any suggestions how I could accomplish that? Perhaps something FUSE-related?