Editing Data integrity (section)

=== Physical integrity ===
Physical integrity deals with challenges which are associated with correctly storing and fetching the data itself. Challenges with physical integrity may include [[electromechanics|electromechanical]] faults, design flaws, material [[fatigue (material)|fatigue]], [[corrosion]], [[Power outage|power outages]], natural disasters, and other special environmental hazards such as [[ionizing radiation]], extreme temperatures, pressures and [[g-force]]s. Ensuring physical integrity includes methods such as [[Redundancy (engineering)|redundant]] hardware, an [[uninterruptible power supply]], certain types of [[RAID]] arrays, [[radiation hardened]] chips, [[ECC memory|error-correcting memory]], use of a [[clustered file system]], using file systems that employ block level [[checksum]]s such as [[ZFS]], storage arrays that compute parity calculations such as [[exclusive or]] or use a [[cryptographic hash function]] and even having a [[watchdog timer]] on critical subsystems.

Physical integrity often makes extensive use of error detecting algorithms known as [[error-correcting codes]]. Human-induced data integrity errors are often detected through the use of simpler checks and algorithms, such as the [[Damm algorithm]] or [[Luhn algorithm]]. These are used to maintain data integrity after manual transcription from one computer system to another by a human intermediary (e.g. credit card or bank routing numbers). Computer-induced transcription errors can be detected through [[hash functions]].

In production systems, these techniques are used together to ensure various degrees of data integrity. For example, a computer [[file system]] may be configured on a fault-tolerant RAID array, but might not provide block-level checksums to detect and prevent [[silent data corruption]]. As another example, a database management system might be compliant with the [[ACID]] properties, but the RAID controller or hard disk drive's internal write cache might not be.