There are some chassis solutions and other solutions. Some provide full bisection bandwidth, some much less, but are much cheaper. The usual way to link together separate boxes is gigabit ethernet. The easiest way to back up a TB is to not back up most of your disks. I only back up the developer's home directories, and not system or scratch disks.
Exabyte are the other contenders.
DAT has a low transfer rate that usually makes it less than useful for big disks. You can pretty much assume 100 watts per normal PC or 200 watts for one of the new 21264 Alphas. When buying UPSes, be sure to not be too optimistic. Big machines show you your little mistakes in the large. If buying from a vendor, insist on a long warrantee.