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Geographic redundancy corrects the vulnerabilities of redundant devices deployed by geographically separating backup devices. Geographic redundancy reduces the likelihood of events such as power outages, floods, HVAC failures, lightning strikes, tornadoes, building fires, wildfires, and mass shootings disabling most of the system if not the entirety of it.
In computer main memory, auxiliary storage and computer buses, data redundancy is the existence of data that is additional to the actual data and permits correction of errors in stored or transmitted data.
System-level soft errors occur when the data being processed is hit with a noise phenomenon, typically when the data is on a data bus. The computer tries to interpret the noise as a data bit, which can cause errors in addressing or processing program code. The bad data bit can even be saved in memory and cause problems at a later time.
A cyclic redundancy check (CRC) is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to digital data. [ 1 ] [ 2 ] Blocks of data entering these systems get a short check value attached, based on the remainder of a polynomial division of their contents.
Some file formats, particularly archive formats, include a checksum (most often CRC32) to detect corruption and truncation and can employ redundancy or parity files to recover portions of corrupted data. Reed-Solomon codes are used in compact discs to correct errors caused by scratches.
Redundancy (information theory), the number of bits used to transmit a message minus the number of bits of actual information in the message; Redundancy in total quality management, quality which exceeds the required quality level, creating unnecessarily high costs; The same task executed by several different methods in a user interface
This is known as N-model redundancy, where faults cause automatic fail-safes and a warning to the operator, and it is still the most common form of level one fault-tolerant design in use today. Voting was another initial method, as discussed above, with multiple redundant backups operating constantly and checking each other's results.
Fail active operational can be installed on systems that have a high degree of redundancy so that a single failure of any part of the system can be tolerated (fail active operational) and a second failure can be detected – at which point the system will turn itself off (uncouple, fail passive).