No one (outside Amazon) truly knows what Glacier is on, likely it is a combination, and tape may play a role, that's why it's relatively inexpensive to house the data, but the costs to get it back are very high and are for "emergency, everything else has failed" situations.
Asked what IT equipment Glacier uses, Amazon told ZDNet it does not run on tape. "Essentially you can see this as a replacement for tape," a company spokesman said via email.
