All about hard drives

Most current computers include at least one hard drive. However, as an internal component, it is often not clear what a hard drive PC is. Furthermore, new technologies do introduce new devices, which are also named hard drives. This article will explain what a hard drive is.

Basics

A hard drive is a device where information is stored in a static way. Upon the removal of the mains power, the data is still remaining, it will not go lost. This is the main difference between hard drives and volatile memory, such as RAM. Since they store the information in a way that can be recovered at each start-up of the system, they are used to keep working data, files, the applications and operating system itself. Currently, there are two main families of hard drives: magnetic (with moving parts inside) and flash drives.

Magnetic storage hard drives

One of the oldest computer technologies in place is based in a similar concept as audio tapes: a set of rotating discs, covered with a magnetisable surface, they are read and written by a moving head (in the same fashion as vinyl needles, but without physical contact). These assembly of disk to disk and read or write heads are inside most current 3.5in and 2.5in drives. This is in most computers and laptops worldwide. As a mature technology, achieved data density is very high, being three terabytes which is the current state-of-the-art in capacity. The main drawback is the fragility of the system which is very sensitive to vibration and shock.

Static memory

Modern semi-conductor technologies allow for the creation of low-cost static memory, in the so-called CMOS and NAND techniques. By using same addressing concepts as in magnetic storage, huge capacities are also available and are still one step behind. The main advantage is the increased read and write speed, since the system does not need to wait for a disc to reach its nominal speed or for the head to locate over the right disc sector. Furthermore, current consumption is also lowered in these flash drives, which increases battery life in portable equipment. Thus, hard drives USB (also known as thumb drives, memory keys) have become a cheap solution for data transport and transfer. Latest technologies are improving this static memory concept, so that SSD (Solid-State Disc) are emerging in the computer market which is still too expensive, but a clear option for quick booting systems and devices with limited power.