To able to backup the server on to a ftp most dedicated server have limited gb, but Web-servers have unlimited space. i hope you understand. my files is like 1 gb.
Why would you need a plugin to do this? Also, it depends on what ftp client/control panel you're using. I thought most minecraft control panels supported backups
because i end up having 50 gb hard-disk space used up in 3 days in just on backups on 100 gb dedicated server limited space. so i have to move them manually to the web-server which has unlimited space. sorry bad english.
50GB of backups? LOL. Why don't you use Subversion? My server world is currently 1.74GB. I have automatic Subversion backups twice a day and each backup is ~70MB on average, relative to how many chunks have changed since the last backup. Three months of daily to bi-daily backups stored in just 10.7GB. I don't even have to restart my server to backup and it only takes seconds.
It's true backup is depend on FTP server, If you are used backup for one computer that time FTP is not require. But you want to backup two or more place that time server require and server is depend on FTP. So that it's true, backup a whole server on FTP.