From Fruk: MySync allows the system to store multiple FTP server profiles (so you can back up different directories to different servers) and folders. The files are scanned, uploaded, and a CRC32 hash of their content stored in a database. The next time you run your backup, the files are scanned again, any changes in the files will result in changes to their CRC32 hash and the file is re-uploaded. Any un-changed files will not be sent to the server again.
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