Hard Disk Drive Internals

A hard disk drive is constructed using four main components, which must all be working correctly, for it to function properly. The four components are the hard disk platters, the read/write heads, motor assembly and the hard disk controller, each performing an essential part of the overall operation. Failure of any of these components can lead to erratic behaviour, leading to additional problems, and require a professional data recovery solution.

Hard Disk Platters

These are the most important part of the disk, as they contain the data stored in magnetic form. The platters are usually an aluminium, glass or ceramic substrate, both sides of which a thin coating is made mostly using a vacuum deposition process called magnetron sputtering. The coating consists of complex layers of metal alloys, which optimise the magnetic media layer. Over this, is a protective carbon-based layer upon which, a lubricant overcoat is deposited. A set of buffing processes are used to remove any defects, as extreme smoothness, durability, and perfection of finish are required properties of a hard-disk platter.

Read/Write Heads

The disk read/write heads move above the disk platter and convert the platter’s magnetic field into electrical current (reading the disk) or transform electrical current into a magnetic field (write to the disk). The hard drive heads ‘fly’ above the surface, with a clearance as small as 3 nanometres. The lower this ‘flying’ distance, the higher the magnetic recording density, which can be achieved. With the head slider containing the head is an air bearing, which maintains the ‘flying’ height at a constant distance. If the head hits the surface of the disk platter, a catastrophic head crash will be the result, requiring data recovery.

Spindle Motor Assembly

The spindle motor assembly, sometimes referred to as the spindle shaft, is responsible for spinning the hard disk platters at a reliable and constant fixed speed. The speeds for different drives range from 4800 rpm through to 15000 rpm for high end SCSI hard disks. Heat and vibration are the biggest issue for a spindle motor, and cause many of the hard disk failures we see arriving at DiskEng for data recovery.

Hard Disk Controller

The hard disk controller performs several functions, all essential for the proper functioning of the hard disk drive. It is responsible for ensuring that the spindle motor assembly spins at the correct speed, that the read/write heads are positioned correctly for each input/output operation and as the interface between the hard disk drive and the host adaptor in the computer.

All Hard Disk Failure Requires Data Recovery

Whichever component fails, it is essential that the drive is powered down as soon as practicable, to avoid a cascade of failures, which in the worst cases involves the read/write heads impacting with the disk platters. All work undertaken to recover data from a failed drive should be undertaken by a professional data recovery company, such as DiskEng, who can address all the problems encountered.

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