Redundant: Difference between revisions
From Computer History Wiki
Jump to navigationJump to search
Redundancy is used throughout engineering |
Add data networking examples |
||
| Line 1: | Line 1: | ||
'''Redundancy''' is a widely-used approach for making things [[robust]] (i.e. resistant to failure or attack); it involves having more than one of a thing ('''redundant''' copies). This can be an expensive approach to achieving that property (e.g. a bridge can be made robust against failure by providing a second complete, parallel, bridge), but it is fairly simple to do, and will work through almost all kinds of failure of the initial copy. | '''Redundancy''' is a widely-used approach for making things [[robust]] (i.e. resistant to failure or attack); it involves having more than one of a thing ('''redundant''' copies). This can be an expensive approach to achieving that property (e.g. a bridge can be made robust against failure by providing a second complete, parallel, bridge), but it is fairly simple to do, and will work through almost all kinds of failure of the initial copy. | ||
In data storage (both [[main memory|primary]], and [[secondary storage]]), it is done by retaining additional information, stored with the basic data. If any of the data is corrupted, the redundant information can be used to recover from the loss. | In data storage (both [[main memory|primary]], and [[secondary storage]]), it is done by retaining additional information, stored with the basic data. If any of the data is corrupted, the redundant information can be used to recover from the loss. Examples there include: | ||
Examples include: | |||
* [[LINC tape]] implements straightforward redundancy by providing duplicates of all the tracks on the [[magnetic tape|tape]]; | * [[LINC tape]] implements straightforward redundancy by providing duplicates of all the tracks on the [[magnetic tape|tape]]; | ||
* [[Random Access Memory|RAM]] targeted for reliable services is protected by [[error-correcting code]]s; | * [[Random Access Memory|RAM]] targeted for reliable services is protected by [[error-correcting code]]s; | ||
* [[RAID]] can mirror [[disk]]s, or add [[Error-correcting code|ECC]]. | * [[RAID]] can mirror [[disk]]s, or add [[Error-correcting code|ECC]]. | ||
In [[data network]]ing, examples include: | |||
* [[retransmission]], used in [[reliable byte stream]] [[protocol]]s, and elsewhere; | |||
* the [[Domain Name System]] makes heavy use of redundancy. | |||
[[Category: Basics]] | [[Category: Basics]] | ||
[[Category: Device Basics]] | [[Category: Device Basics]] | ||
Latest revision as of 11:37, 3 November 2026
Redundancy is a widely-used approach for making things robust (i.e. resistant to failure or attack); it involves having more than one of a thing (redundant copies). This can be an expensive approach to achieving that property (e.g. a bridge can be made robust against failure by providing a second complete, parallel, bridge), but it is fairly simple to do, and will work through almost all kinds of failure of the initial copy.
In data storage (both primary, and secondary storage), it is done by retaining additional information, stored with the basic data. If any of the data is corrupted, the redundant information can be used to recover from the loss. Examples there include:
- LINC tape implements straightforward redundancy by providing duplicates of all the tracks on the tape;
- RAM targeted for reliable services is protected by error-correcting codes;
- RAID can mirror disks, or add ECC.
In data networking, examples include:
- retransmission, used in reliable byte stream protocols, and elsewhere;
- the Domain Name System makes heavy use of redundancy.
