Editing Disk array controller (section)

== Enterprise controllers ==
{{main|Disk array}}
In a modern enterprise architecture disk array controllers (sometimes also called '''storage processors''', or '''SPs'''<ref>{{Cite web|url=http://vmtoday.com/2010/03/storage-basics-part-v-controllers-cache-and-coalescing/|title = Storage Basics - Part V: Controllers, Cache and Coalescing|date = 23 March 2010}}</ref>) are parts of physically independent [[disk enclosure|enclosure]]s, such as [[disk array]]s placed in a [[storage area network]] (SAN) or [[network-attached storage]] (NAS) [[Server (computing)|server]]s.

Those external disk arrays are usually purchased as an integrated subsystem of RAID controllers, disk drives, power supplies, and management software. It is up to controllers to provide advanced functionality (various vendors name these differently):
* Automatic [[failover]] to another controller (transparent to computers transmitting data)
* Long-running operations performed without [[downtime]]
** Forming a new RAID set
** Reconstructing ''degraded'' RAID set (after a disk failure)
** Adding a disk to online RAID set
** Removing a disk from a RAID set (rare functionality)
** Partitioning a RAID set to separate volumes/LUNs
* [[snapshot (computer storage)|Snapshots]]
* [[Business continuance volume]]s (BCV)
* [[disk mirroring|Replication]] with a remote controller....