RSYNC is an open source utility that provides fast incremental file transfer. It should actually be written in a lower case like "rsync"...

This is a great tool to use for synchronizing large directories of files. Imagine that you run a couple of servers in a remote office far, far away... How do you back up the data to your headquarters?

Typically you would install an incremental backup solution. After incremental backup is created in the remote office you would transfer it to the main office. File transfer is fast, but someone has to reassamble old backup and incremental backup into a single image. This takes extra disk space and extra time.

Alternatively you could create a full backup and then transfer it. Now you will by paying a lot for the Internet traffic. You can also cause traffic jam in the remote office routers, firewalls, etc.

You could use RSYNC instead. It has benefits of incremental transfer and does not need reassembly step. Follow this plan:

• create a secure channel between the remote office and the main office; use VPN or SSH
• run an instance or RSYNC in the remote office
• run an instance or RSYNC in the main office
• specify file sets that need synchronization
• let RSYNC to do incremental file transfer

RSYNC will save you Internet traffic cost. It is free! It has been around for a while. It can be fully automated, scheduled, etc. It really works!