From: Disk

This area moves WAY too fast for me to keep up with all of the
products and announcements; ideally, it should teach enough about
principles and other information sources to allow users to find the
information they need.

Quantum has a good educational web site, with info on the history and
technology of disk drives, at
http://www.quantum.com/src/storage_basics/toc.html.

A lot of spec sheets for recent disk drives (when they say they also
have "old drives", they mean early 90s, not 50s-80s) is available at
http://www.blue-planet.com/tech/index.html.  Looks like a good site.