Data degradation

Not to be confused with software rot.

Data degradation, also known as data decay or data rot, is a colloquial computing phrase for the gradual decay of storage media. It should not be confused with "bit rot", defined in the Jargon File as a jocular explanation for the degradation of a software program over time even if "nothing has changed".[1]

Decay of data in memory

Data degradation in dynamic random-access memory (DRAM) can occur when the small electric charge of a bit in DRAM disperses, possibly altering program code or stored data. Semiconductor RAM may also occasionally be altered by cosmic rays or other high-energy particles; such data degradation is known as soft errors.[2] Different variants of ECC memory can be used to mitigate this type of data degradation.

Decay of storage media

Data degradation can also be used to describe the phenomenon of storage media gradually decaying over the duration of many years. The cause of data decay varies depending on the medium:

Component and system failures

Most disk, disk controller and higher-level systems are subject to a small degree of unrecoverable failure. With ever-growing disk capacities, file sizes, and increases in the amount of data stored on a disk, the likelihood of the occurrence of data decay and other forms of uncorrected and undetected data corruption increases.[3]

Higher-level software systems may be employed to mitigate the risk of such underlying failures by increasing redundancy and implementing integrity checking and self-repairing algorithms.[4] The ZFS file system was designed to address many of these data corruption issues.[5] The Btrfs file system also includes data protection and recovery mechanisms,[6] and so does ReFS.[7]

See also

References

  1. Raymond, Eric. "Bit rot". The Jargon File. Retrieved 3 March 2013.
  2. O'Gorman, T. J.; Ross, J. M.; Taber, A. H.; Ziegler, J. F.; Muhlfeld, H. P.; Montrose, C. J.; Curtis, H. W.; Walsh, J. L. (January 1996). "Field testing for cosmic ray soft errors in semiconductor memories". IBM Journal of Research and Development 40 (1): 41–50. doi:10.1147/rd.401.0041. Retrieved 4 March 2013.
  3. Gray, Jim; van Ingen, Catharine (December 2005). "Empirical Measurements of Disk Failure Rates and Error Rates" (PDF). Microsoft Research Technical Report MSR-TR-2005-166. Retrieved 4 March 2013.
  4. Salter, Jim (15 January 2014). "Bitrot and atomic COWs: Inside "next-gen" filesystems". Ars Technica. Archived from the original on 23 March 2015. Retrieved 15 January 2014.
  5. Bonwick, Jeff. "ZFS: The Last Word in File Systems" (PDF). Storage Networking Industry Association (SNIA). Retrieved 4 March 2013.
  6. "btrfs Wiki: Features". The btrfs Project. Retrieved 19 September 2013.
  7. Wlodarz, Derrick. "Windows Storage Spaces and ReFS: is it time to ditch RAID for good?". Betanews. Retrieved 2014-02-09.
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