This article is from the storage FAQ part2, by Rodney D. Van Meter with numerous contributions by others.
They have some agreement with Legent Corporation. OSM runs on Sparc machines, including the Cray Superservers. Price ranges from $500 to $5,000, which is very cheap for HSM. However, it might only be capable of migrating among disks -- I don't see any mention of autochangers. (rdv, 94/12/9)