remote backup solution over WAN

[S t i n g r a y]

I am building one backup file server on WAN on FreeBSD, which will backup remote servers data over slow links, (256-512kbps), simply because i have never seen an operating system as stable/robust as FreeBSD ever :-)
Now i want to know a technology that can sync only the changed data in a day rather then all the data daily, keep in mind the remote servers data would be  Windows, Linux and Apple computers so the technology must be compatible with all ... 

 


regards


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