DeltaSCP
DeltaSCP allows you to transfer deltas of files and block devices, instead of copying them entirely.
Suppose you have hard disks you want to back up, say, LVM snapshots or virtual machine disk images. It will transfer only the changes between the local and remote copies of these block devices. For example, if you have a 64GB virtual machine hard drive, the first time using DeltaSCP, it will transfer the entire thing. The next time you do the same copy, though, it will transfer only the changes, plus its overhead (roughly 1/1365, in this example 48MB).
DeltaSCP operates like the SSH tool scp, and uses SSH. Install it on both the local and remote machines, and then, you can use it just like scp:
| deltascp /my/file/ me@1.2.3.4:/target/file |
DeltaSCP also supports rate limiting, so if you have a slow connection or do not want to otherwise disrupt your Internet connection while performing backups, you can do this. As an example, this will limit the transfer to 384 kilobits per second:
| deltascp -a 384 me@1.2.3.4:/target/file /my/file |
While it was created for backing up block devices, it is able to transfer files as well. If the target of the copy is anything that *cannot* be resized, its size must match the source.
Also included is DeltaDD, a lower level tool you may use if you want to send deltas over something other than SSH.
DeltaSCP is distributed as source code. You will need OpenSSL development packages installed to compile it.
DeltaSCP uses the ISC license.