What is a “Bad Sector”

A “Bad Sector” is a term for a broken piece of Hard Disk Drive (HDD)–a very small piece. There are millions of sectors on a hard drive. EG, standard sector size is 512 bytes (aka 512B). Consider a typical disk (in 2015) of 1TB in size, or 1,000,000,000,000 bytes (1 trillion bytes). Doing some math: there are 2 million sectors on a 1TB hard drive.

That means everything you store on there is broken up into pieces of 512. Have a 100MB video file? It is stored as 2000 pieces of 512B each.

Fortunately, when sectors go bad, two mechanisms exist to help you.

  1. The hard disk drive itself detects many bad sectors and remaps them so that data is stored elsewhere, in good sectors. You may never notice these.
  2. Windows Operating System detects bad sectors and marks them to avoid using them in the future. Windows Vista, 7, 8 (and presumably 10 and later) detect when a “chkdsk” is necessary and prompt you to run it at next boot. If not, you can run “chkdsk” yourself.

Note: when the OS detects hard disk errors, you should IMMEDIATELY MAKE A BACKUP. DO NOT PASS GO. DO NOT COLLECT $200.

Then, get a new hard drive.

Usually things will only get worse. In the upcoming months, even days, even hours.

Why do sectors go bad?

Reference: https://en.wikipedia.org/wiki/Disk_sector

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