Editing RAID (section)

{{Short description|Data storage virtualization technology}}
{{About|the data storage technology|the police unit|RAID (French police unit)|other uses|Raid (disambiguation)}}

'''RAID''' ({{IPAc-en|r|eɪ|d}}; '''redundant array of inexpensive disks''' or '''redundant array of independent disks''')<ref name="patterson"/><ref name="RAB" /> is a data [[storage virtualization]] technology that combines multiple physical [[Computer data storage|data storage]] components into one or more logical units for the purposes of [[data redundancy]], performance improvement, or both. This is in contrast to the previous concept of highly reliable mainframe disk drives known as ''single large expensive disk'' (''SLED'').<ref name="Katz" /><ref name="patterson">{{Cite conference |last1=Patterson |first1=David |author1-link=David Patterson (computer scientist) |last2=Gibson |first2=Garth A. |author2-link=Garth A. Gibson |last3=Katz |first3=Randy |author3-link=Randy Katz |year=1988 |title=A Case for Redundant Arrays of Inexpensive Disks (RAID) |publisher=SIGMOD Conferences |url=https://www2.eecs.berkeley.edu/Pubs/TechRpts/1987/CSD-87-391.pdf |access-date=2024-01-03}}</ref>

Data is distributed across the drives in one of several ways, referred to as [[RAID levels]], depending on the required level of [[redundancy (engineering)|redundancy]] and performance. The different schemes, or data distribution layouts, are named by the word "RAID" followed by a number, for example RAID&nbsp;0 or RAID&nbsp;1. Each scheme, or RAID level, provides a different balance among the key goals: [[reliability engineering|reliability]], [[availability]], [[computer performance|performance]], and [[computer data storage#Capacity|capacity]]. RAID levels greater than RAID&nbsp;0 provide protection against unrecoverable [[Disk sector|sector]] read errors, as well as against failures of whole physical drives.