This article is from the storage FAQ part2, by Rodney D. Van Meter with numerous contributions by others.
From Advanced Archival Products. Supports a huge range of devices, autochangers, and operating systems. Block-based movement of data between the hard disk cache and tape or optical tertiary storage. Systems run from a few gigabytes up to at least 12 TB, with prices dependent on capacity. New versions allow multiple cache disks. Slips right in to the VFS layer and looks like a normal Unix file system, with the plusses and minuses that entails. No file versioning or multiple copies yet. File creation is an Achilles' heel on performance. Since it's block based, files can be larger than a piece of media. Separate product DataMgr will migrate files from client machines to the AMASS server automatically (with FS changes, of course). AMASS is now owned by EMASS, and you can find info at http://www.emass.com/Products/Software_Products/AMASS/AMASS_Top.html. (rdv, 1996/3/27)