the anatomy of a hard drive.

The platters are the part of the hard drive that contains all of the data on a thin layer of metal alloy coating. The surfaces of the platters are completely flat. The magnetic field of tiny portions of this coating determines which parts of the disks are “0”s and which are “1”s. Hard drive platters have billions of these regions per each surface of the platter, and hard drives have several platters inside them. The tiny read/write heads inside a hard drive, hover just a few nanometers above the platters and pick up or alter the magnetic signals given off from the platters. In order for the heads to do their job properly, the platters have to be perfectly smooth. A slightly raised area on a platter’s surface, for example - a little bit of dust - can be devastating. If the heads make contact with the platters at any time, they can scratch a part of the thin layer of metal coating that holds the data. To recover data from a hard drive with scratched platters, the platters must be carefully extracted from the hard drive’s chassis in a data recovery clean air lab and any embedded particles must be removed. In most cases, the read/write heads, which are usually responsible for scratching the platters, must be replaced. Sometimes the damage is so bad that the entire chassis must be replaced.