Hard disk drive

Hard disk drive

The mechanism that reads and writes data on a hard disk. Hard disk drives (HDDs) for PCs generally have seek times of about 12 milliseconds or less. Many disk drives improve their performance through a technique called caching.

There are several interface standards for passing data between a hard disk and a computer. The most common are IDE and SCSI.

Hard disk drives are sometimes called Winchester drives, Winchester being the name of one of the first popular hard disk drive technologies developed by IBM in 1973.

Once known as the Winchester drive, the hard disk or hard drive is an essential hardware that every computer desktop and server contain. And its functionality, is to store vast amount of digital data in a non-volatile form, so that data can be retained when the computer is powered off. Data is again accessed when the power is on.

How Does A Hard Disk Work?

If you are to dismantle the hard disk drive by opening the top casing (after removing all the necessary screws), the first thing you'll see is a spindle holding one or a number of mirror-like hard rotating platters (commonly called data platter). The platters could be made to spin at an extremely high speed, technically between 5,400 to 10,000 revolutions per minute (RPM). An extremely thin magnetic coating is layered onto the surface of the platter that is polished to mirror-type smoothness. The platter is usually made of glass or ceramic (modern platter may use titanium). Unlike a floppy disk, the platter cannot be bent or flipped and hence we coin it as "hard disk" or "hard drive".

Commonly a hard disk contains 1 to 10 identical platters that are stacked in parallel to form a cylinder. There is usually one Read Write (RW) head designated per platter face, and each head is attached to a single actuator shaft which moves all heads in unison and performs a uniform synchronous motion during reading or writing of data. Data on a hard disk is stored in microscopic areas called magnetic domains on the magnetic material. Each domain stores either a 1 or 0 value. Similar to a floppy disk, a hard disk records its data in concentric circles or tracks, which are numbered from the outermost edge to the innermost edge of the platter. These tracks are further subdivided into smaller units called sectors which typically store 512 bytes of data each. Zoning may be needed to further optimise the data storage as the outer circumference would normally pack more sector units than the inner circumference. 

 

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kinds of hard drive

Hard disks can be found in a variety of devices: desktops, notebooks, servers, Microdrive CompactFlash slot is plugged in, embedded in an MP3 player.
Although the cage of different ways of working and construction of hard disk everywhere are basically the same. However not all devices are easily dismantled to know more about your hard disk in it. Microdrive and hard disk in MP3 too small, rare servers, and notebooks are relatively difficult touched.
Meaning your hard disk is a disk or hard disk. As their name the hard disk consists of a collection plate (different from the floppy disk that had only one disc) with a surface coated with a thin film magnetic material. The term film in the world usually means a layer of material engineering. His relationship with moving images? Ordinary movie is stored in a thin layer of celluloid.
Thin film magnetic material is spread on top of another material called a substrate. Formerly common metals such as aluminum is used as substrate, but the hard disk is currently using advanced composite glass or glass / ceramic.
The advantages of using glass is a dish that is more thinner and lighter. It also means the motor only requires minimal power to rotate the dish. Depending on its design-makers could use a second hard disk or the disk surface is just one.
This thin film storing all digital information in the form of magnetic patterns. All of the information. Read. and the. written. using a component called the head. Functions the same as the head on a tape recorder, that is to vary the polar magnetic spots on thin-film hard disk.
Discs that contain a thin film is collected and turned by the shaft which in English is called the spindle. All the discs are rotated by the motor in high speed.
Motor rotation speed varies for each model of the hard disk. On the desktop computer's hard disk disk rotational speed reaches 7200 rpm and on the server even reach 15 000 rpm (rotation per minute.putaran per minute, ppm). Hitachi Microdrive has made speed 3600 rpm.
The number of discs in a single hard disk can be diverse, ranging from single dish to reach 6 disc. But usually the hard disk maker to limit the number of discs used.
Create a clear micro hard disk size is not desirable. But with developments in technology make possible micro hard disk size.
Some of the reasons that make the dish more interesting small, even for a desktop computer are:
Resilience of the dish.Smaller discs are more resistant to shock and vibration compared to large-sized disc. Hard disks contained in an MP3 player will be more robust than hard disks in desktop computers. In the small resistance problem is far more superior than the Giant.
Ease of manufacture.Disc-quality hard disk should be smooth without any defects. Easier to meet this demand for micro plate. Power saving. Small discs have a lighter mass.
This means that power consumption is required to play it is also lower. It definitely helps businesses save battery in handheld devices.
Performance.Smaller discs to reduce the distance covered head to find the necessary data. This means faster access times and improved overall performance of your hard disk.
Seeing all these reasons clear the hard drive makers will be competing to shrink their products. But the miniaturization of hard disks are not easy matters. There are several obstacles that must first be overcome.In addition to the difficulties faced in making a very small component of other important issues is how to increase the data density per unit area (area density).