NERSC: Proving Tape as Cost-Effective and Reliable Primary Data Storage

When is tape a direct access storage device? And when is a very active tape archive really just another tier of "regular" storage?  At the NERSC Center in California, tape is simply seen as extremely efficient, cost-effective, scalable-and reliable-storage. With over 13 PB of data on tape (growing at around 60% p.a.) and decades of history, NERSC has the facts to prove tape's capabilities; so much so that it does not employ additional copies.