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What Is a RAID Controller? A Basic Definition

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RAID stands for redundant array of independent disks. This is a type of data storage virtualization technology that lumps physical disk drive components together to drive data redundancy and/or improvement.

A RAID card manages a PC’s hard disk drives or solid-state drives (SSDs) so that they work together and drive redundancy and/or performance. It can be hardware (a RAID card) or software.

There are different types of RAID, as dictated by the Storage Networking Industry Association.

Common RAID Levels

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  • RAID 0 - evenly distributes data across at least two disks without parity bit information, redundancy and fault tolerance
  • RAID 1 - makes a copy of data on at least two disks without parity information, striping or spanning disk space across multiple disks
  • RAID 5 - distributes data across two or more disks with distributed parity
  • RAID 6 - same as RAID 5 but with one more parity block (a form of data storage)

Less Common RAID Levels:

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  • RAID 2 - distributes data evenly in bits, rather than blocks
  • RAID 3 - byte-level striping with a parity disk
  • RAID 4 - block-level striping with a parity disk

Nested RAID Levels

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There are also RAID levels combining two or more of the above RAID levels. For example, RAID 0+1 (aka RAID 01) and RAID 0+3 (aka RAID 03).

This article is part of the Tom's Hardware Glossary.

Further Reading: