The development of magnetic disk drives has seen dramatic advances in the last few years, far outstripping the convention of Moore's Law (g) and, in addition, the standards that define the connection between hard disk drives and computers have also been added to in the last five years.

There are two key 'dimensions' of change in hard disk technology; capacity and cost. The capacity increases very quickly at any given price point. However, for a given capacity, the price drops quickly as well. Sometimes lower cost also leads to lower reliability as well, but in systems relying on low cost, high capacity storage, such risks that lower reliability brings are offset by building in redundancy, by using more cheap storage.

Up to a point, a system can have smaller disks replaced by larger disks without causing too much disruption, but eventually the increase in size causes pressure to be applied elsewhere in a system. Just as an increase in, for instance, your car's engine size would eventually put a greater strain on the gearbox and transmission, so the use of increasingly large storage capacity places strains on the IT network connections that support them.

We have another section of this tutorial looking at Network Connection Standards (T2-1-2-6), but at a smaller scale, the connections to the actual disk drives are managed by the Back Plane(T2-1-2-5).