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How does a hard drive work?

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Quick answer

A hard drive works by storing data as microscopic magnetized spots on spinning platters. A tiny arm with a read/write head flies just above the surface, flipping and reading the magnetic direction of each spot to write and retrieve 1s and 0s.

Step by step

  1. Data lives as magnetic patterns on rapidly spinning disks (platters).
  2. A read/write head on a moving arm hovers nanometers above the surface.
  3. Magnetizing a spot one way stores a 1, the other way a 0.
  4. To read, the head detects each spot's magnetic direction as the platter spins beneath it.
  5. Mechanical parts make it slower and more fragile than an SSD, but cheaper per gigabyte.

People also ask

Why are hard drives slower than SSDs?
The head must physically move and the platter must spin to the right spot, adding mechanical delay an all-electronic SSD avoids.
What happens if you drop a hard drive?
A shock can make the head strike the platter (a 'head crash'), scratching the surface and destroying data — SSDs have no such risk.
Why are hard drives still used?
They cost much less per gigabyte than SSDs, so they remain popular for bulk storage and backups.