HARD DISK DRIVE
Data storage has become a daily activity for everyone since we have PCs. In our daily life, we use, as the most important center of data storage, our PC. The hard disk drive (HDD) in the “data center” of the PC. It is here that all the programs and data that we use are stored. The hard disk is the most important of the various types of permanent storage used IN PCs. The HDD differs from others (floppy disks, CD ROMS, removal drives etc) especially in three ways: size (usually larger), speed (usually faster) and permanence (usually fixed in PC and not removable).
Hard disk drive stores and provides quick access to large amounts of data. This, and the fact of providing a personal data storage, is the reason for why the HDD are one of the most important data centers.
The progress that HDDs have made in term of capacity, speed and price in the last twenty years can be denominate as amazing.
HDDs were created in 1956 as data storage for an IBM accounting computer and were originally developed for computer´s use. In first place, HDDs were removable, and the first HDD was one tone weigh and had the size of an actual fridge. The big success of this invent was that you could access a specific piece of information directly, without rolling and unrolling.
Thanks of discovering the magnetic resistance (MR) by Albert Fert and Peter Grunberg (both winners of the physics Nobel), the capacity of HDDs increases enormously (60% per year during the 1990 decade).
The first PC hard disk had a capacity of 10 MB and cost over $100 per MB. Modern hard disks have capacities approaching 100 GB and cost less than 1 cent per MG.
In the 21st century, HDD usage expanded into consumers applications such as camcorders, cell phones (ex: Nokia N91), digital video player…
HDDs record data by magnetizing ferromagnetic material directionally, to represent either a 0 or a 1 binary digit. They read the data back by detecting the magnetization of the material. A typical HDD design consists of a spindle that holds one or more flat circular disks called platters, onto which the data is recorded.
The platters are spun at very high speeds. Information is written to a platter as it rotates past devices called read-and-write heads that operate very close (tens of nanometers in new drives) over the magnetic surface. The read-and-write head is used to detect and modify the magnetization of the material immediately under it. There is one head for each magnetic platter surface on the spindle, mounted on a common arm.
As data density increased, read heads using magnetic resistance (MR) came into use; the electrical resistance of the head changed according to the strength of the magnetism from the platter. Later development made use of spintronics; in these heads, the magnetoresistive effect was much greater than in earlier types, and was dubbed "giant" magnetic resistance (GMR). In today's heads, the read and write elements are separate, but in close proximity, on the head portion of an actuator arm. The read element is typically magneto-resistive while the write element is typically thin-film inductive.
HDDs are very fast because they don´t have mobile parts and consume less energy. All of this makes them very reliable and almost indestructible.
Nowadays, the new generation of HDDs uses the perpendicular recording technology that allows a bigger density of storage. As well, there exist disk called “ecological” (GP- Green Power) that uses less energy.
However, it is starting to be seeing that it is possible that the “solid state drive” (SSD) finish by replacing the HDDs in the long term.
References:
http://www.monografias.com/trabajos/discoduro/discoduro.shtml
http://www.discoduro.org/
http://es.wikipedia.org/wiki/Disco_duro
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