Toms Hardware Guide published an article about the evolution of the hard drive, including benchmarking tests that bolt old hardware (circa 1991) to modern PCs. In the last 15 years, storage density has increased 10,000x!
It’s worth a read, particularly for the graphics and narrative about how hard drive technology has evolved. I thought the graphic showing the evolution of storage from 1960 (the graphic on their website is munged, but the data is there) to today. It’s clear that Magneto-Resistive (MR) technology was a crucial development, as the graph knees right at that point.
The article examines in depth the relationship between storage density and the bandwidth to that storage (known as ‘storewidth’) and how the bandwidth has failed to keep pace.
While this fact causes problems for general computing (and why Vista can now use flash memory to accelerate boot times), I believe that latent information (giant databases) and media (access is not random) have been the primary drivers for more storage capacity and are not as sensitive to access speeds.
Anyway, there’s lots of good raw data in the article that will get your wheels turning after a holiday break.