Storage capacity
Performance testing is our bread and butter, but it's far from the only element to the storage equation. Capacity counts for a lot, and that's where we've seen some of the biggest gains over the years.

The anemic capacity of early SSDs skews the above graph some, but if you just pay attention to the yellow bars, it's clear that the storage capacity of mechanical hard drives has grown by leaps and bounds. Back when we started using this test system, the biggest hard drive in the market weighed in at 250GB. Today, that's half the capacity of just one of a 2TB Caviar Green's four platters.

An eightfold increase in 3.5" storage capacity in less than five years is quite an achievement. The capacity of 2.5" notebook drives has grown, too, from a maximum of just 100GB to a half-terabyte today.

I have a soft spot for Western Digital's 10k-RPM Raptors, and it's worth noting that these drives have jumped in capacity from just 37GB at launch to 300GB with the latest VelociRaptor. What makes this nearly order-of-magnitude increase so impressive is the fact that the new VelociRaptor is a 2.5" drive (although not thin enough to fit in most notebooks) while the rest of the Raptor family are of the much larger 3.5" variety.

SSDs may be the new hotness, but storage capacity remains their greatest challenge. 256GB is a long, long way from 2TB. And that's before considering the cost per gigabyte. Of course, solid-state drives have other strengths.