How Hard Disks Works ?

oday We are going to discuss about how hard disk works.Hard Disk is an important part of Computers, without it, you can not imagine the computer. But most of us don't know how it works, so this post is made especially for you.


If you are to uncover 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 say 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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