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Hard Drive Operation and Common Causes of Failure

What is a Hard Drive?

A hard drive (HD) is the component of a computer that stores and retrieves information and programs, such as an individual’s files and operating system. The hard drive’s physical components are a plastic or metal disk, read/write head(s) for reading and writing data on the disk, and platters for storing the data. The read/write head is attached to a moving arm called a seek ramp. An electric motor controls the movements of the arm and the platters.

How Hard Drives Work

The most basic configuration of an HD consists of a single hard disk, a spindle motor, a head arm assembly, and a read/write electronics package. Many HD drives are used in conjunction with a host computer system. This host computer system typically includes a power supply, a motherboard, memory, a central processing unit, and peripherals. All of the host computer system components are connected to the HD drive with a cable.

HD drives operate in the following manner to store and retrieve data on the disk: a disk spins when powered on, and the read/write head moves over the platters. The arm moves so that the head is over the exact location where data is to be read or written. The read/write circuit then uses the read/write head to read or write data from the drive. This process, known as reading or writing, occurs in the time it takes for the disk to rotate one complete revolution.

Common Causes of Hard Drive Failure

A HD failure is anything that causes the hard drive not to work as designed, meaning data cannot be stored or retrieved. A HD may fail because of:

  • A manufacturing defect
  • When the arm assembly is broken or not correctly aligned with the spindle, the drive cannot read or write correctly. Also, if the arm assembly is improperly installed, the drive will not spin on startup.
  • A HD often fails because of the read/write (r/w) head, which is a component that reads or writes data to the data storage platter. The r/w head may be damaged by a power surge or from exposure to a magnetic field. 
  • Physical contact between the r/w heads and the hard drive platter is another way a hard drive can fail. An r/w head crash usually occurs when the head crashes into the platter. 
  • Power surges also cause the r/w heads to move improperly. Causes of power surges include lightning strikes, electrostatic discharge, or brownouts.
  • The heads can also be damaged by overheating. For example, excessive heat can cause the head to stick to the platter, damaging the head.
  • Mechanical damage can also cause the heads to fail.
  • Water damage
  • Software corruption

Signs The Hard Drive May Be Near Failure

If you notice any of these events, you should take action quickly to avoid loss of data:

  • Clicking, loud sounds, or unusual noises
  • Slow performance
  • Upon boot up, you see a message about checking the hard drive or correcting errors on the hard drive
  • Your computer occasionally ‘locks up’ or freezes unexpectedly


Common causes of hard drive failure include manufacturing defects, power supply failure, overheating, physical damage, or a combination of these. The most common cause of hard drive failure is physical damage, such as being dropped, placed in a backpack while turned on, or mishandled in ways that cause harm. Mechanical damage can also cause the drive to fail, such as the failure of the motor or the read/write head. Other causes include electrical problems with the logic board inside the hard drive.

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