RAID - Revision history

Jnc: 'RAID: A Personal Recollection' - another copy

2024-12-06T11:48:12Z

'RAID: A Personal Recollection' - another copy

← Older revision		Revision as of 11:48, 6 December 2024
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	* RAID 6 - a virtual drive is striped across multiple physical drives, with replicated, distributed ECC		* RAID 6 - a virtual drive is striped across multiple physical drives, with replicated, distributed ECC

	==See also==		<!-- ==See also==
			-->
	==External links==		==External links==

	* [https://www2.eecs.berkeley.edu/Pubs/TechRpts/1987/CSD-87-391.pdf A Case for Redundant Arrays of Inexpensive Disks (RAID)]		* [https://www2.eecs.berkeley.edu/Pubs/TechRpts/1987/CSD-87-391.pdf A Case for Redundant Arrays of Inexpensive Disks (RAID)]
	* [http://web.eecs.umich.edu/~michjc/eecs584/Papers/katz-2010.pdf RAID: A Personal Recollection of How Storage Became a System]		* [http://web.eecs.umich.edu/~michjc/eecs584/Papers/katz-2010.pdf RAID: A Personal Recollection of How Storage Became a System] <!-- https://annals-extras.org/anecdotes/writing/katz-on-raid.pdf -->
	* [https://minnie.tuhs.org/cgi-bin/utree.pl?file=V6/usr/man/man4/rk.4 rk.4] - 'striping' in UNIX V6		* [https://minnie.tuhs.org/cgi-bin/utree.pl?file=V6/usr/man/man4/rk.4 rk.4] - 'striping' in UNIX V6

	[[Category: Device Basics]]		[[Category: Device Basics]]

Jnc: /* Types */ typo

2023-09-07T11:18:48Z

Types: typo

← Older revision		Revision as of 11:18, 7 September 2023
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	==Types==		==Types==

	Different RAID schemes are referred to by labels of the form 'RAID n', where n is a digit; all produce a single virtual drive. RAID 2-6 all use an [[error-correcting code\|ECC]], and are able to recover from damage to a single physical drive. In RAID 2-4, the ECC information is stored on a single other drive; in RAID 5 and 6, it is stored om multiple drives.		Different RAID schemes are referred to by labels of the form 'RAID n', where 'n' is a digit; all produce a single virtual drive. RAID 2-6 all use an [[error-correcting code\|ECC]], and are able to recover from damage to a single physical drive. In RAID 2-4, the ECC information is stored on a single other drive; in RAID 5 and 6, it is stored on multiple drives.

	The main ones are:		The main ones are:

	* RAID 0 - a virtual drive is split across multiple physical drives; provides increased performance only		* RAID 0 - a virtual drive is striped (split) across multiple physical drives; provides increased performance only
	* RAID 1 - a virtual drive is mirrored across multiple physical drives; provides increased reliability only		* RAID 1 - a virtual drive is mirrored across multiple physical drives; provides increased reliability only
	* RAID 2 - a virtual drive is striped across multiple physical drives, a [[bit]] at a time		* RAID 2 - a virtual drive is striped across multiple physical drives, a [[bit]] at a time

Jnc: ECC location; example of striping in early UNIX

2023-08-20T16:30:16Z

ECC location; example of striping in early UNIX

← Older revision		Revision as of 16:30, 20 August 2023
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	==Types==		==Types==

	Different RAID schemes are referred to by labels of the form 'RAID n', where n is a digit; all produce a single virtual drive. RAID 2-6 all use an [[error-correcting code\|ECC]], and are able to recover from damage to a single physical drive~~; in~~ RAID 2-4, the ECC information is stored on a single other drive.		Different RAID schemes are referred to by labels of the form 'RAID n', where n is a digit; all produce a single virtual drive. RAID 2-6 all use an [[error-correcting code\|ECC]], and are able to recover from damage to a single physical drive. In RAID 2-4, the ECC information is stored on a single other drive; in RAID 5 and 6, it is stored om multiple drives.

	The main ones are:		The main ones are:
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	* [https://www2.eecs.berkeley.edu/Pubs/TechRpts/1987/CSD-87-391.pdf A Case for Redundant Arrays of Inexpensive Disks (RAID)]		* [https://www2.eecs.berkeley.edu/Pubs/TechRpts/1987/CSD-87-391.pdf A Case for Redundant Arrays of Inexpensive Disks (RAID)]
	* [http://web.eecs.umich.edu/~michjc/eecs584/Papers/katz-2010.pdf RAID: A Personal Recollection of How Storage Became a System]		* [http://web.eecs.umich.edu/~michjc/eecs584/Papers/katz-2010.pdf RAID: A Personal Recollection of How Storage Became a System]
			* [https://minnie.tuhs.org/cgi-bin/utree.pl?file=V6/usr/man/man4/rk.4 rk.4] - 'striping' in UNIX V6

	[[Category: Device Basics]]		[[Category: Device Basics]]

Jnc: Quick overview

2023-08-20T15:52:36Z

Quick overview

New page

'''RAID''' (originally an acronym for 'redundant array of inexpensive disks'; later redefined to stand for 'redundant array of independent disks') is the name for a family of schemes to increase the reliability, performance or size of [[disk]] [[mass storage]] by using a number of [[drive]]s in parallel.

The basic ideas pre-date the original definition of the term (below): early [[UNIX]] disk [[device driver]]s had split a single virtual drive across multiple physical drivers ('striping'); and mirrored disks (for reliability) had been used by [[Tandem]].

==Types==

Different RAID schemes are referred to by labels of the form 'RAID n', where n is a digit; all produce a single virtual drive. RAID 2-6 all use an [[error-correcting code|ECC]], and are able to recover from damage to a single physical drive; in RAID 2-4, the ECC information is stored on a single other drive.

The main ones are:

* RAID 0 - a virtual drive is split across multiple physical drives; provides increased performance only
* RAID 1 - a virtual drive is mirrored across multiple physical drives; provides increased reliability only
* RAID 2 - a virtual drive is striped across multiple physical drives, a [[bit]] at a time
* RAID 3 - a virtual drive is striped across multiple physical drives, a [[byte]] at a time
* RAID 4 - a virtual drive is striped across multiple physical drives, a block at a time
* RAID 5 - a virtual drive is striped across multiple physical drives, with distributed ECC
* RAID 6 - a virtual drive is striped across multiple physical drives, with replicated, distributed ECC

==See also==

==External links==

* [https://www2.eecs.berkeley.edu/Pubs/TechRpts/1987/CSD-87-391.pdf A Case for Redundant Arrays of Inexpensive Disks (RAID)]
* [http://web.eecs.umich.edu/~michjc/eecs584/Papers/katz-2010.pdf RAID: A Personal Recollection of How Storage Became a System]

[[Category: Device Basics]]