Home › Devices & Everyday Tech › Data Backup & Cloud Storage › redundancy

redundancy

rih-DUN-duhn-see /rɪˈdʌn.dəns.i/

nounC1GREGMATCAT

technicalprofessional

The inclusion of extra, duplicate components or systems that are not strictly necessary to functioning, but exist to ensure continued operation in case of a failure.

In everyday speech, redundancy means being useless or laid off from a job. In tech, however, redundancy is highly positive—it means having a safety net so that if one server or hard drive dies, another instantly takes over.

The story behind the word. Redundancy comes from the Latin redundare, meaning 'to overflow' or 'to rise in waves' (from unda, meaning wave). Originally, it described water overflowing a container. In computing, it represents data overflowing its primary home into secondary systems to ensure nothing is lost.

Word relationships

duplication: Duplication is simply making a copy, whereas redundancy is a deliberate engineering design where duplicate systems are ready to take over during a failure.
superfluity: Superfluity means an excess of something that is unnecessary and wasteful, whereas technical redundancy is highly purposeful and protective.

singularity: The state of being singular, which in engineering represents a single point of failure where no backup exists.

Commonly confused with

backup: A backup is a static copy of data that you restore after a failure, while redundancy is an active, parallel system that prevents any downtime from occurring in the first place.

Word family

redundant (adjective): Exceeding what is necessary; repetitive.

Collocations

system redundancy
data redundancy
built-in redundancy
redundancy plan

Example sentences

"The data center features multiple power grids and network connections to provide maximum redundancy." Explaining high-availability cloud infrastructure.
"By using a redundant array of independent disks, the server can survive the physical failure of a hard drive without losing data." Designing a secure storage array.

Memory hook

Think of 'waves' (unda) washing over a beach. One wave follows another in a repetitive, redundant pattern to ensure the shore is always wet. Redundancy is having a spare tire already spinning on the car.

When not to use

Do not use redundancy to describe a simple backup that must be manually restored; redundancy implies an active, automatic failover system.

Fun facts

NASA's Space Shuttle used five redundant onboard computers running identical software. If one computer disagreed with the others, the system would ignore it and rely on the majority consensus.