What Is Rsync Backup?Rsync is a software application for UNIX and UNIX based operating systems. It is used to synchronize files and directories from one location to another while minimizing data transfer using delta encoding when appropriate. Naturally rsync backup has a lot of appeal to those interested in corporate data protection and the protection of customer privacy. A data protection company interested in keeping files confidential can use rsync backup to safely secure files to ensure there is a backup up in case of a disaster while also making sure that the data is still as securely held as the original. Rsync is free software licensed under the GNU General Public License. The algorithm (formula) behind rsync backup was developed by Australian computer programmers Andrew Tridgell and Paul Mackerras in the mid 1990's. Version 3.0 of rsync was released on March 1st, 2008. Rsync backup's algorithm efficiently transmits a structure (such as a file) across a communication link when the receiving computer already has a different version of the same structure. The recipient splits its copy of the file into fixed-size non-overlapping chunks and computes two checksums for each chunk: the MD4 hash, and a weaker "rolling checksum." It sends these checksums to the sender. The sender computes the "rolling checksum" for every chunk of size S in its own version of the file, even overlapping chunks. This can be calculated efficiently because of a special property of the "rolling checksum": if the "rolling checksum" of bytes n through n + S - 1 is R, the rolling checksum of bytes n + 1 through n + S can be computed from R, byte n, and byte n + S without having to examine the intervening bytes. So if you had already calculated the "rolling checksum" of bytes 1-25, you could calculate the "rolling checksum" of bytes 2-26 solely from the previous checksum, and from bytes 1 and 26. Rsync's algorithm forms the heart of the rsync backup application. It essentially optimizes transfers between two computers over TCP/IP. The rsync backup application supports other features that aid significantly in data transfers or backup. These include compression and decompression of data block by block using zlib at sending and receiving ends, respectively. Support for protocols such as ssh that enables encrypted transmission of compressed and efficient differential data using rsync algorithm is also offered. Instead of ssh, stunnel can also be used to create an encrypted tunnel to secure the data transmitted. |