100 Tb its not going to be cheap. Would definately go to dedicated file server with a blade set up. I work on some massive networks but not neede 100tb of storage.

I look after (sort of) a mac enviroment, about 40 g5s that do video editing and a serios amount of music editing and production. they use a mac server cant remeber storage amount but they have individual back up drives on each mac that the individual backs up at the end of the week and that can be removed.

Dunno if that helps but 100tb back up facilities will not be cheap...