How Do Disc Drives Work? A Technology Guide

How Do Disc Drives Work? A Technology Guide

by Bryn Fest

IBM developed the first disc drive in 1956. It had a 24″ diameter and a storage capacity of 3.75 megabytes.

Until recently storage for electronics meant a hard disc drive or an optical disc drive. SSDs are taking over now since they are smaller and fit inside tinier devices.

For decades disc drives were how you stored data and programs. Have you ever wondered how exactly those little metal boxes managed such a feat? Keep reading to learn the answer to the question, “How does a disc drive work?” and so much more!

Hard Disc Drives

Disc drive technology is based on storing data on platters of glass, or aluminum, covered with a thin layer of magnetic material. The platters are held by a central spindle. Each platter spins at up to 10,000 RPMs and has millions and even billions of tiny areas that hold specific magnetic orientations.

As the platters spin, a stepper motor moves actuator arms over the platters. At the end of each actuator arm resides a magnet that detects the magnetic orientation (north to south or south to north) of each area, where each orientation represents either a 0 or a 1.

If you would like to learn more about magnets and how you can use them, click here.

Data are stored in binary code across circular tracks around the discs and are further segregated into sectors. Your device software has a file allocation table (FAT) that keeps track of the data. Think of the FAT like the glossary of a book: it knows where every bit lies on the disc.

A controller board resides between the disc drive motor and the software of your computer and acts as a translator converting the language of the computer into instructions the hard drive motor understands.

Optical Disc Drives

Optical drives took a while longer to appear in the history of disc drives, and while similar to HDDs in many ways, such as using platters to store data, they are unlike HDDs in that the platters get inserted by the user.

The most common types of platters are CDs, DVDs, and Blu-ray discs.

While there are versions of these discs you can write to, they are uncommon, and optical platters are primarily used as “read-only.”

Optical discs read data from platters using a laser. Each type of platter requires a different wavelength of light to read the data from the disc.

  1. CDs use 780 nanometers (infrared) of light
  2. DVDs use 650 nanometers (red) of light
  3. Blu-Rays use 405 nanometers (violet) of light

More on Optical and Magnetic Disc Drives

Optical drives, unlike HDDs, spin at varying speeds. This is to deliver data at a constant rate, given that the data will take longer to arrive under the laser the closer it is to the edge of the platter. This constant rate of delivery is vital for smooth movie and music enjoyment.

Optical drives are typically used for inserting data into a computer from an outside source: think computer program installations, movies, and music. Hard drives are more often used to hold installed programs as well user data.

Based on Simple Ideas

Disc drives are based on magnetics and the simplest numerical system: binary. Combining these with stepper motor technology, engineers designed a device to hold complex data in practically any form imaginable.

When you bring up a picture of a dog on your screen, that was created by a stream of 0s and 1s represented by magnetic poles read by a magnet.

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