I totally Agree that Tape isnt the optimal solution(nor is it very flexible with that amount of data), but i can in no way endorse a solution to disk, if its in the same physical datacenter as the production data is stored.
The point of my advice was more in line with.. get the data out of the datacenter for your backups, and if a extra datacenter is cost prohibtive, i suggest tape, to have the possibility to move it out.
Ofcause disk based backup is a more sane solution when we are talking those kind of volumes, but if you just keep it in a rack next to your production data, your happy fellowed if the place is destroyed.
Who knows what is possible from the limited amount of info
Deduplication alone, will reduce the backup window, and recovery time by Alot. But is it fesible to do?
Hope you understand Q.