iDisk is .Mac’s storage service, which is (at best) moderately useful for sharing files and (at worst) a mess.

Based on WebDAV, it is most likely the least useful feature of .Mac and has a number of serious issues that completely put me off it, namely:

  1. It transmits all your data without any encryption
  2. It only performs integral file updates (i.e., it does not allow for partial file updates, like rsync)
  3. It is excruciatingly slow, regardless of where you are and what kind of access you have at your disposal

…all of which makes it completely useless for any sort of serious off-site backup. And it does not take kindly to storing encrypted disk images, since even the .sparsebundle format falls afoul of its limitations.

Known Good Alternatives

Using MacFUSE and SSH is way faster, and there are alternative services like S3 that only need a decent UI (there’s JungleDisk, but that has mixed reviews, and I’d like to have more options).

What I think someone should do

Still, the best approach is likely to be for someone to put together a mirroragent replacement that can talk rsync over SSH to a standard UNIX system.

Or a decent Mac OS X GUI and preference pane for rdiff-backup, which is pretty stable, or duplicity, which has the added benefit of storing the backups in encrypted form (making it possible for me to use just about any machine I want to).

Assorted Notes

Reclaiming space (from here):

hdiutil unmount ~/Library/FileSync/*/*.sparsebundle
hdiutil compact ~/Library/FileSync/*/*.sparsebundle