This article is from the storage FAQ part2, by Rodney D. Van Meter with numerous contributions by others.
NSL is an industry consortium (American companies only) that has a version of Unitree, and is creating their own new High Performance Storage System. HPSS, among other features, supports striping of removable media, and full 64-bit files. Some of the work is being done at LLNL, where UniTree was originally developed. There's a good overview reachable at http://www.ccs.ornl.gov/HPSS/HPSS.html. (rdv,95/1/12)