Bad sector

As a defective data block (English Bad Block ) is called when storage media such as hard disks, floppy disks or flash memories, an unusable, ie for writing and reading operations no longer usable, the data block.

Defective data blocks occur due to manufacturing defects, however, may also arise at run time due to wear and aging. Also erroneous write operations can cause data blocks are marked as bad. In the event there is software that can remove the selection again. If defective data blocks in a memory, this does not necessarily mean its complete failure. A software component in the hard disk firmware or flash drive can replace the defective memory blocks via a mapping table by error-free blocks of memory from a reserve area automatically. This process is known as remapping and carried out by a known as a defect block management (English Bad Block Management System) software component.

The test performed at remapping logical assignment to the actual, physical memory blocks enables transparent access to the data blocks of a memory - to accept without regard to its physical defects. As long as the reserve area is not yet exhausted, the memory can be used without restrictions.

Accumulate defective data blocks conspicuous so is a serious mechanical defect surface with hard disks - usually caused by a head crash - to be expected. To prevent data loss, the hard disk in question should be replaced as soon as possible.

A measure of security against surface defects and thus to read and write errors in floppy is the clipping level.

• Digital storage medium