Anybody familiar with incremental backup knows that the de facto standard of backup utilities is a program called rsync. This is an unfortunate truth for Windows user's however because rsync is primarily a unix/linux application. DeltaCopy is a Windows backup program that takes advantage of rsync.

The application comes packaged as either an installer or stand-alone deal. Deltacopy is distributed in a client-server model, so you have to run both the client app and the server if you want to do local backups (backing up to two local drives, as opposed to a drive on another computer).

The backend of Deltacopy (rsync) is really what makes this application shine. Rsync uses a number of principles to make the backup process much faster. First it uses an incremental backup algorithm. This means that after the initial backup process is run, successive backup processes only back up data that has changed since the last time the process was run (this is an over-generalization as incremental backup can be much more complex than this). So how does rsync know if certain files have been modified? Well, there are a couple of ways. First, whenever a file is opened and modified, potentially several of its attributes can change, but most importantly (at least to a backup program), the last modified date and file size likely change. Rsync compares these attributes with files that have already been backed up and only updates files that have been modified.

Another way rsync makes backup fast and efficient is by only updating the contents of a file that has changed. So for instance, if I have a large disc image of a DVD I have backed up to my computer and I recently changed the name of the file or modified its contents, rsync wouldn't re-copy the entire file, it would only make the changes to the file it needed to (I'm fairly certain that I have understood this concept properly, but if not, please leave a comment with correction).

Another way rsync makes the backup process speedy is by compressing files before they are transferred. This is really helpful if you are copying to another computer either over a local network or over the internet as remote file transfer is much slower than local transfer. The smaller the file size (compressed) the smaller the transfer time.

Other Screenshots: