The best way to do this would be to create a replica or a DFS on Windows. But that is not by far the most cost effective. If you have a gigabit network and an identical array to mirror that would be great but chances are you are going to be backing up to a LTO3 Tape library using something like Arcserve or Veritas. Each tape can hold about 800gb compressed so you could do it with a single LTO3 drive if you are willing to swap the tapes out.
<a href=”http://www.google.com/products?hl=en&safe=off&client=firefox-a&rls=org.mozilla:en-US:official&hs=Lhe&q=lto3+&um=1&ie=UTF-8&sa=X&oi=product_result_group&resnum=1&ct=title”>You can find purchasing options here for the lto3′s.</a>
You can then backup using a differential or full backup and rotate the tapes every so often. It all comes down to what your environment and budget are.