powers of four

To cope with SLAC's vast arsenal of facts and figures, the computing department houses six data silos containing collectively around twenty-two thousand 200-gigabyte tapes, and around five thousand 20-gigabyte tapes. Though they are slower than disks, tapes are better for long term archival of data and more durable. Now, the six tape-based data silos are being replaced with newer, more compact storage structures.

Wow, I had no idea there was so much data stored at SLAC... even so, the storage challenges of future scientific projects taking place at SLAC would vastly exceed this capacity.