What is disk sector?

In the context of computer hardware, a sector is a sub-division of a track of a magnetic hard disk or optical disc. A sector stores a fixed amount of data. The typical formatting of sectors allows holding 512 bytes (e.g. harddisks and diskettes) or 2048 bytes (e.g. optical discs) of data.

What is a bad sector?

A sector is a small area on the surface of a hard drive or a floppy disk.

Hard drives usually have several platters. The platters are the discs which are covered with magnetic material which is used to hold data. Floppy disk drives contain only one platter.

Platters are divided into a set of concentric rings called tracks. A 1.44MB floppy disk has 160 tracks. Hard drives have thousands of tracks.

Each of these tracks is divided into smaller storage areas called sectors. A sector is the smallest storage area on a disk.

What is a Bad Sector?

Hard drives are contain millions of sectors. It is very normal for some of these sectors to be bad sectors, even when the drive is first manufactured.

In addition, a small number of sectors will normally go bad during the lifespan of a drive.

When this happens, the data in those sectors may be lost, but the data on the rest of the disk will be unaffected and the disk is still completely usable.

A bad sector cannot be repaired, but it can be marked as unusable. Once marked as unusable, the Operating System will know not to attempt to store data in that bad sector. The storage capacity of the disk will be decreased by the amount of storage space in the bad sector.

If your hard drive develops a bad sector, back the hard drive up immediately. If the bad sector was caused by a faulty drive head, the problem can quickly spread to other sectors on the disk.

How to repair a bad sector?

1. Full format a partition

Right click “My Computer” > “Manage” > “Storage” > “Disk Management”, right click the partition and select Format. Or open “My Computer”, right click the partition, and then select Format.

Note: the default format option in Windows XP is Full Format, but in Windows 7, it is Quick Format. After full format in Windows 7, you cannot recover files.

2. CHKDSK command

Press Start > Run, input “cmd”, input “chkdsk X: /r” (X is the drive letter)

3. Press the <Start> button.

  • Select <My Computer>.
  • Under Hard Disk Drives highlight the disk which you want to scan.
  • Open the <File> menu and choose <Properties>
  • Open the <Tools> tab.
  • Click the <Check Now…> button.

In earlier version of Microsoft Windows and DOS, this functionality was built into the “scandisk” and “chkdsk” utilities.

Once the bad sector or sectors have been “repaired”, continue to back up your hard drive on a regular basis. Hard drives are mechanical devices and all mechanical devices will eventually fail.

You’d better diagnose your hard drive regularly, you may refer HDD Diagnose software and HDD monitor software for more info.

Learn more about hdd tool

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