To answer your question:
At Dartmouth all digitized materials are backed up in streaming formats on CD
ROM, and, more recently, on DVD-R. They also "live" on a pair of mirrored
servers. All audio files we have are also backed up on CD-R/DVD-R in MP3 format
on a restricted server. We have kept all master tapes. We have also kept tape
sets for lab use for those languages that require the Record/Playback function
of an analog recorder. We'll toss those out once DL Recorder is ready for prime
time throughout the network here.
We have seen reel to reel tapes recently that literally dumped their oxide on
the heads of the last professional deck we have (purchased from eBay!). We
expect the same to happen to cassette tape and to video tapes. So archiving the
tape media to optical media really makes sense.
The only reason for not tossing out the cassettes is probably proof of
ownership... and oh, did we have the rights to transfer to another media because
the original media was crumbling away? But that's an entirely different
issue!....
Otmar Foelsche