T 4.7 Defective data media

All types of data media can fail, become damaged, or contain errors in the data. This can become a problem when the information stored on the data media is not saved anywhere else and cannot be reconstructed quickly and easily. In terms of data losses, total losses of data are less common when using analogue data media than when using digital data media. People, unlike computers, are able to read information from half-burnt or torn paper documents without requiring complex tools or additional aids.

Unfortunately, it is relatively common for individual data media to fail or to contain errors in the data stored on them due to technical defects or damage. Susceptible media include mass storage devices like hard disks, tapes, and cartridge systems. Hard disks can be destroyed when the read/write head crashes, and tapes and cartridges can be damaged by direct mechanical impact. CD-ROMs and DVDs can be rendered useless by surface scratches.

Examples:

• In a medium-sized company, a large amount of dust was produced due to construction work. Particles of dust even penetrated the computer room and found their way into the hard disk of a server. The result was a head crash that destroyed some of the data.

• A field service employee's laptop inexplicably started failing occasionally even though it was always carefully packed before transportation. It turned out that the hard disk of the laptop had been damaged by a magnet used to secure a folding table in a train.
• Some ZIP diskettes were temporarily stacked on the speakers of a multimedia PC while backing up the data on the PC. The magnets in the speakers erased some sections of data on the data media.

• Bit errors on archived data media can mean that it may be impossible to decrypt encrypted documents. It may also be impossible to verify digital signatures due to bit errors.