ON-LINE Backup

Hi all,
I?m studing a way to improve backup and data security for my company.
To do this, apart from the normal Backup, I?m thinking about putting a simple file server on the same LAN with an on-line mirror of the working file server.

Can you point a Linux distribution and an app with sync capabilities? I?m reading abou rsync and other but I don?t know how reliable are them.

A Windows version is also a possibility, altough it could be more expensive.

Thanks in advance for any help you can give!
P. Val