Editing RAID (section)

===<span class="anchor" id="SOFTWARE"></span><span class="anchor" id="RAID-F"></span>Software-based===
Software RAID implementations are provided by many modern [[operating system]]s. Software RAID can be implemented as:

* A layer that abstracts multiple devices, thereby providing a single [[Virtualization|virtual device]] (such as [[Linux kernel]]'s [[mdadm|md]] and OpenBSD's softraid)
* A more generic logical [[volume manager]] (provided with most server-class operating systems such as [[Veritas file system|Veritas]] or [[Logical Volume Manager (Linux)|LVM]])
* A component of the file system (such as [[ZFS]], [[IBM Spectrum Scale|Spectrum Scale]] or [[Btrfs]])
* A layer that sits above any file system and provides parity protection to user data (such as RAID-F)<ref>{{Cite web|url=http://www.flexraid.com/faq-items/what-is-raid-over-file-system/|title=RAID over File System|access-date=2014-07-22|archive-date=2013-11-09|archive-url=https://web.archive.org/web/20131109055927/http://www.flexraid.com/faq-items/what-is-raid-over-file-system/|url-status=dead}}</ref>

Some advanced [[file system]]s are designed to organize data across multiple storage devices directly, without needing the help of a third-party logical volume manager:

* [[ZFS]] supports the equivalents of RAID&nbsp;0, RAID&nbsp;1, RAID&nbsp;5 (RAID-Z1) single-parity, RAID&nbsp;6 (RAID-Z2) double-parity, and a triple-parity version (RAID-Z3) also referred to as RAID&nbsp;7.<ref>{{cite web|title=ZFS Raidz Performance, Capacity and Integrity|url=https://calomel.org/zfs_raid_speed_capacity.html|website=calomel.org|access-date=26 June 2017}}</ref> As it always stripes over top-level vdevs, it supports equivalents of the 1+0, 5+0, and 6+0 nested RAID levels (as well as striped triple-parity sets) but not other nested combinations. ZFS is the native file system on [[Solaris (operating system)|Solaris]] and [[illumos]], and is also available on FreeBSD and Linux. Open-source ZFS implementations are actively developed under the [[OpenZFS]] umbrella project.<ref>{{cite web |url=http://wiki.illumos.org/display/illumos/ZFS |title=ZFS -illumos |publisher=[[illumos.org]] |date=2014-09-15 |access-date=2016-05-23 |archive-date=2019-03-15 |archive-url=https://web.archive.org/web/20190315183042/https://wiki.illumos.org/display/illumos/ZFS |url-status=dead }}</ref><ref>{{cite web|url=http://docs.oracle.com/cd/E23823_01/html/819-5461/gaypw.html |title=Creating and Destroying ZFS Storage Pools – Oracle Solaris ZFS Administration Guide |publisher=[[Oracle Corporation]] |date=2012-04-01 |access-date=2014-07-27}}</ref><ref>{{cite web |url=http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/filesystems-zfs.html |title=20.2. The Z File System (ZFS) |website=freebsd.org |access-date=2014-07-27 |url-status=dead |archive-url=https://web.archive.org/web/20140703043231/http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/filesystems-zfs.html |archive-date=2014-07-03 }}</ref><ref>{{cite web|url=http://docs.oracle.com/cd/E19120-01/open.solaris/817-2271/gcviu/index.html |title=Double Parity RAID-Z (raidz2) (Solaris ZFS Administration Guide) |publisher=[[Oracle Corporation]] |access-date=2014-07-27}}</ref><ref>{{cite web|url=http://docs.oracle.com/cd/E19120-01/open.solaris/817-2271/givdn/index.html |title=Triple Parity RAIDZ (raidz3) (Solaris ZFS Administration Guide) |publisher=[[Oracle Corporation]] |access-date=2014-07-27}}</ref>
* [[IBM General Parallel File System|Spectrum Scale]], initially developed by IBM for media streaming and scalable analytics, supports [[Non-standard RAID levels#Declustered RAID|declustered RAID]] protection schemes up to n+3. A particularity is the dynamic rebuilding priority which runs with low impact in the background until a data chunk hits n+0 redundancy, in which case this chunk is quickly rebuilt to at least n+1. On top, Spectrum Scale supports metro-distance RAID&nbsp;1.<ref>{{Cite web|title=General Parallel File System (GPFS) Native RAID|url=http://www.usenix.org/events/lisa11/tech/slides/deenadhayalan.pdf|first=Veera|last=Deenadhayalan|publisher=[[IBM]]|website=UseNix.org|year=2011|access-date=2014-09-28}}</ref>
* [[Btrfs]] supports RAID&nbsp;0, RAID&nbsp;1 and RAID&nbsp;10 (RAID&nbsp;5 and 6 are under development).<ref>{{cite web|title = Btrfs Wiki: Feature List|date = 2012-11-07|access-date = 2012-11-16|url = https://btrfs.wiki.kernel.org/index.php/Main_Page#Features}}</ref><ref>{{cite web|title = Btrfs Wiki: Changelog|date = 2012-10-01|access-date = 2012-11-14|url = https://btrfs.wiki.kernel.org/index.php/Changelog}}</ref><!--Although in Wiki format, this is documentation and changelog used by btrfs, a GPL project-->
* [[XFS]] was originally designed to provide an integrated volume manager that supports concatenating, mirroring and striping of multiple physical storage devices.<ref>{{cite web
 |archive-date=2015-04-22
 |archive-url=https://web.archive.org/web/20150422201638/http://linux-xfs.sgi.com/projects/xfs/papers/xfs_white/xfs_white_paper.html
 | url = http://linux-xfs.sgi.com/projects/xfs/papers/xfs_white/xfs_white_paper.html
 | title = Scalability and Performance in Modern File Systems
 | access-date = 2015-08-17
 | first1 = Philip | last1 = Trautman | first2 = Jim | last2 = Mostek
 | website = linux-xfs.sgi.com
}}</ref> However, the implementation of XFS in Linux kernel lacks the integrated volume manager.<ref>{{cite web
 | url = https://raid.wiki.kernel.org/index.php/RAID_setup#XFS
 | title = Linux RAID Setup – XFS
 | date = 2013-10-05 | access-date = 2015-08-17
 | website = kernel.org
}}</ref>

Many operating systems provide RAID implementations, including the following:

* [[Hewlett-Packard]]'s [[OpenVMS]] operating system supports RAID&nbsp;1. The mirrored disks, called a "shadow set", can be in different locations to assist in disaster recovery.<ref>{{cite web |url=https://support.hpe.com/hpsc/doc/public/display?docId=emr_na-c04619764 |title=HPE Support document - HPE Support Center |author=Hewlett Packard Enterprise |website=support.hpe.com}}</ref>
* Apple's [[macOS]] and [[macOS Server]] natively support RAID&nbsp;0, RAID&nbsp;1, and RAID&nbsp;1+0,<ref>{{cite web |url=http://support.apple.com/kb/TA24359 |title=Mac OS X: How to combine RAID sets in Disk Utility |access-date=2010-01-04}}</ref><ref>{{cite web |url=https://www.apple.com/server/macosx/technology/file-system.html |title=Apple Mac OS X Server File Systems |access-date= 2008-04-23}}</ref> which can be created with [[Disk Utility]] or its [[command-line interface]], while RAID&nbsp;4 and RAID&nbsp;5 can only be created using the third-party software ''SoftRAID'' by [[Other World Computing|OWC]],<ref>{{cite web |url=https://www.techpowerup.com/320611/other-world-computing-launches-softraid-8-setting-a-new-standard-for-reliability-speed-and-data-safeguards |title=Other World Computing Launches SoftRAID 8 Setting a New Standard for Reliability, Speed and Data Safeguards |publisher=TechPowerUp |date=2024-03-20 |access-date=2024-11-24 }}</ref> with the driver for SoftRAID access natively included since [[macOS Ventura|macOS 13.3]].
* [[FreeBSD]] supports RAID&nbsp;0, RAID&nbsp;1, RAID&nbsp;3, and RAID&nbsp;5, and all nestings via [[GEOM]] modules and ccd.<ref>{{cite web |url=http://www.freebsd.org/cgi/man.cgi?query=geom |title=FreeBSD System Manager's Manual page for GEOM(8) |access-date=2009-03-19}}</ref><ref>{{cite web |url=http://lists.freebsd.org/pipermail/freebsd-geom/2006-July/001356.html |title=freebsd-geom mailing list – new class / geom_raid5 |date=6 July 2006 |access-date=2009-03-19}}</ref><ref>{{cite web |url=http://www.freebsd.org/cgi/man.cgi?query=ccd |title=FreeBSD Kernel Interfaces Manual for CCD(4) |access-date=2009-03-19}}</ref>
* [[Linux]]'s [[mdadm|md]] supports RAID&nbsp;0, RAID&nbsp;1, RAID&nbsp;4, RAID&nbsp;5, RAID&nbsp;6, and all nestings.<ref>{{cite web |url=http://tldp.org/HOWTO/Software-RAID-HOWTO.html |title=The Software-RAID HowTo |access-date=2008-11-10}}</ref> Certain reshaping/resizing/expanding operations are also supported.<ref>{{cite web |title=mdadm(8) – Linux man page |url=http://linux.die.net/man/8/mdadm |website=Linux.Die.net |access-date=2014-11-20}}</ref>
* [[Microsoft Windows]] supports RAID&nbsp;0, RAID&nbsp;1, and RAID&nbsp;5 using various software implementations. [[Logical Disk Manager]], introduced with [[Windows 2000]], allows for the creation of RAID&nbsp;0, RAID&nbsp;1, and RAID&nbsp;5 volumes by using [[dynamic disks]], but this was limited only to professional and server editions of Windows until the release of [[Windows 8]].<ref>{{Cite web |url=http://support.microsoft.com/kb/923332/ |title=Windows Vista support for large-sector hard disk drives |date=2007-05-29 |website=Microsoft |url-status=dead |archive-url=https://web.archive.org/web/20070703092408/http://support.microsoft.com/kb/923332/ |archive-date=2007-07-03 |access-date=2007-10-08}}</ref><ref>{{Cite web |url=http://support.microsoft.com/kb/927520/en-us |title=You cannot select or format a hard disk partition when you try to install Windows Vista, Windows 7 or Windows Server 2008 R2 |date=14 September 2011 |publisher=[[Microsoft]] |url-status=live |archive-url=https://web.archive.org/web/20110303111057/http://support.microsoft.com/kb/927520/en-us |archive-date=3 March 2011 |access-date=17 December 2009}}</ref> [[Windows XP]] can be modified to unlock support for RAID&nbsp;0, 1, and 5.<ref>{{Cite web |url=http://www.tomshardware.com/reviews/windowsxp-make-raid-5-happen,925.html |title=Using Windows XP to Make RAID&nbsp;5 Happen |date=19 November 2004 |publisher=[[Tom's Hardware]] |access-date=24 August 2010}}</ref> [[Windows 8]] and [[Windows Server 2012]] introduced a RAID-like feature known as [[Storage Spaces]], which also allows users to specify mirroring, parity, or no redundancy on a folder-by-folder basis. These options are similar to RAID&nbsp;1 and RAID&nbsp;5, but are implemented at a higher abstraction level.<ref name="B8_storage_spaces">{{cite web |last=Sinofsky |first=Steven |title=Virtualizing storage for scale, resiliency, and efficiency |url=http://blogs.msdn.com/b/b8/archive/2012/01/05/virtualizing-storage-for-scale-resiliency-and-efficiency.aspx |publisher=Building Windows 8 blog|date=January 5, 2012|access-date=January 6, 2012|archive-date=May 9, 2013|archive-url=https://web.archive.org/web/20130509100721/http://blogs.msdn.com/b/b8/archive/2012/01/05/virtualizing-storage-for-scale-resiliency-and-efficiency.aspx|url-status=dead}}</ref>
* [[NetBSD]] supports RAID&nbsp;0, 1, 4, and 5 via its software implementation, named RAIDframe.<ref>{{cite web |title=NetBSD 1.4 Release Announcement |url=http://www.netbsd.org/releases/formal-1.4/NetBSD-1.4.html |first=Perry |last=Metzger |publisher=The NetBSD Foundation |work=NetBSD.org |date=1999-05-12 |access-date=2013-01-30}}</ref>
* [[OpenBSD]] supports RAID&nbsp;0, 1 and 5 via its software implementation, named softraid.<ref>{{cite web |title=OpenBSD softraid man page |url=https://man.openbsd.org/softraid.4 |access-date=2018-02-03 |website=OpenBSD.org}}</ref>

If a boot drive fails, the system has to be sophisticated enough to be able to boot from the remaining drive or drives. For instance, consider a computer whose disk is configured as RAID&nbsp;1 (mirrored drives); if the first drive in the array fails, then a [[Bootloader|first-stage boot loader]] might not be sophisticated enough to attempt loading the [[booting#Second-stage boot loaders|second-stage boot loader]] from the second drive as a fallback. The second-stage boot loader for FreeBSD is capable of loading a [[kernel (operating system)|kernel]] from such an array.<ref>{{cite web |url=http://www.freebsd.org/doc/en_US.ISO8859-1/books/handbook/geom-mirror.html |title=FreeBSD Handbook |work=Chapter 19 GEOM: Modular Disk Transformation Framework |access-date= 2009-03-19}}</ref>