Actually, a category in itself would be those programs do 'patches' (aka delta backup), that is, they copy/move only the bits of the file that have changed. Any of these delta backup programs should beat traditional ones at speed.Unison
is one of them. Note that the same authors have started a new project: Harmony
. So Unison is kind of unsupported, and looks like something that needs an important time investment.
Commercial software that does delta backup:
Novell's ifolders, According to http://www.ifolder.com/
[ifolder.com]: " iFolder is a simple and secure storage solution that can increase your productivity by enabling you to back up, access and manage your personal files-from anywhere, at any time. Once you have installed iFolder, you simply save your files locally-as you have always done-and iFolder automatically updates the files on a network server and delivers them to the other machines you use. Sponsored by Novell, the iFolder project is built on the Mono/.Net framework to integrate seamlessly into existing desktop environments. ".
The flash presentation says that it uses delta backup, but it is not featured in the description. Problem: only usable acrross the net, no HD backup possible.
It seems that v 3 is OSS, although that must be the server? I dunno, slashdot commentaries here
Another delta backup tool: Suresync
. price=$69, same as SFFSP-WTF
. It does provide real-time syncing and delta backup using an addon (sold separately), I mailed them for a quote.
Looks like it really has lots of features!
Depending on how expensive the addon is, and how unusable/time-consuming Unison is, this could be an interesting pick. It can do HD backups fine.