The hard disk: Maximum memory thanks to minimization

There are many competing names for permanent storage media in the IT sector: Hard disk, hard disk drive (HDD) or simply hard disc (HD). These are magnetic storage media with rotating disks ('platters') on which data is stored without contact.

Recently, solid state drives (SSDs) have also become available that no longer contain any moving parts. Although these are faster, they are also more expensive. They require more energy and offer less storage space. However, because they are less sensitive to shocks, they have conquered the mobile sector in particular (MP3 players, USB sticks, smartphones).

With conventional hard disks, storage capacities in the terabyte range are now also easily available for private customers (currently up to 10 TB). The increase in the storage capacity of HDDs roughly follows the increase in standard market computing power. The current standard size is 3.5".

Conventional hard disks are constructed as follows: One or more magnetizable discs ('platters') are mounted on an axis or spindle on a hydrodynamic plain bearing, a small electric motor drives the spindle (which then causes the typical 'hard disk noise'). Movable read-write heads (in principle tiny electromagnets) on an actuator axis take over the fixation of the data on the platters with the help of control electronics coupled to a digital signal processor (DSP), whereby they float 'contact-free' on the rotating air cushion above the disk. A hard disk cache enables the intermediate storage of data, while an interface ensures communication with other components of the computer. A fixed housing protects the electronics and the sensitive data disks.

The number and coating of the disks, as well as the intelligent type of 'labeling', determine the storage capacity. Today, modern hard disks use High Storage Density Media (HSDM), usually a CoCrPt alloy that is protected from damage by a diamond-like carbon coating. The increasing data density means that intensive research is now being carried out into ultra-high storage density media.

Incidentally, data does not have to be stored 'internally'. Many of our customers use b.r.m.'s external storage capacities - firstly because they have access to the most advanced hard disk technology and secondly because their data is protected from unauthorized access in a 'high-security room'.