Computer data storage: Difference between revisions

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=== Energy use ===

* Storage devices that reduce fan usage automatically shut-down during inactivity, and low power hard drives can reduce energy consumption by 90 percent.<ref>{{cite web|url=http://www.springlightcfl.com/consumer/energy_savings_calculator.aspx|title=Energy savings calculator|url-status=dead|archive-url=https://web.archive.org/web/20081221131054/http://springlightcfl.com/consumer/energy_savings_calculator.aspx|archive-date=21 December 2008}}</ref><ref>{{Cite web|url=http://www.simpletech.com/content/eco-friendly-redrive|url-status=dead|archive-url=https://web.archive.org/web/20080805092907/http://www.simpletech.com/content/eco-friendly-redrive|archive-date=5 August 2008|title=How much of the [re]drive is actually eco-friendly?|website=Simple tech}}</ref>

* 2.5-inch hard disk drives often consume less power than larger ones.<ref>{{cite web|title=IS the Silent PC Future 2.5-inches wide?|url=http://www.silentpcreview.com/article145-page1.html|access-date=2 August 2008|author=Mike Chin|date=8 March 2004|url-status=live|archive-url=https://web.archive.org/web/20080720000101/http://www.silentpcreview.com/article145-page1.html|archive-date=20 July 2008}}</ref><ref>{{cite web|url=http://www.silentpcreview.com/article29-page2.html|title=Recommended hard drives|access-date=2 August 2008|author=Mike Chin|date=18 September 2002|url-status=live|archive-url=https://web.archive.org/web/20080905085853/http://www.silentpcreview.com/article29-page2.html|archive-date=5 September 2008}}</ref> Low capacity [[solid-state drive]]s have no moving parts and consume less power than hard disks.<ref>{{Cite web|url=http://techreport.com/articles.x/10334/13|title=Super Talent's 2.5" IDE flash hard drive|website=The tech report|date=12 July 2006|page=13|archive-url=https://web.archive.org/web/20120126045422/http://techreport.com/articles.x/10334/13|archive-date=26 January 2012|access-date=18 June 2011}}</ref><ref>{{Cite web|url=httphttps://www.tomshardware.com/reviews/conventional-hard-drive-obsoletism,1324-5.html|title=Power consumption – Tom's hardware : Conventional hard drive obsoletism? Samsung's 32 GB flash drive previewed|website=tomshardware.com|date=20 September 2006|access-date=18 June 2011}}</ref><ref name=xbitSSDvsHD/> Also, memory may use more power than hard disks.<ref name=xbitSSDvsHD>{{cite web|title=SSD, i-RAM and traditional hard disk drives|date=23 April 2008|url=http://www.xbitlabs.com/articles/storage/display/ssd-iram.html|author=Aleksey Meyev|publisher=X-bit labs|url-status=dead|archive-url=https://web.archive.org/web/20081218134355/http://www.xbitlabs.com/articles/storage/display/ssd-iram.html|archive-date=18 December 2008}}</ref> Large caches, which are used to avoid hitting the [[memory wall]], may also consume a large amount of power.

=== Security ===

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* '''Redundant array of independent disks''' ('''[[RAID]]''') – This method generalizes the device mirroring above by allowing one device in a group of devices to fail and be replaced with the content restored (Device mirroring is RAID with ''n=2''). RAID groups of ''n=5'' or ''n=6'' are common. ''n>2'' saves storage, when compared with ''n=2'', at the cost of more processing during both regular operation (with often reduced performance) and defective device replacement.

Device mirroring and typical RAID are [[designed]] to handle a single device failure in the RAID group of devices. However, if a second failure occurs before the RAID group is completely repaired from the first failure, then data can be lost. The probability of a single failure is typically small. Thus the probability of two failures in the same RAID group in time proximity is much smaller (approximately the probability squared, i.e., multiplied by itself). If a database cannot tolerate even such a smaller probability of data loss, then the RAID group itself is replicated (mirrored). In many cases such mirroring is done geographically remotely, in a different storage array, to handle recovery from disasters (see disaster recovery above).

=== Network connectivity ===

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== Further reading ==

* {{cite journal|title=The history of storage systems|journal=[[Proceedings of the IEEE]]|author1=Goda, K. |author2=Kitsuregawa, M. |year=2012|pages=1433–1440|volume=100|doi=10.1109/JPROC.2012.2189787|doi-access=free}}

* [httphttps://www.computerhistory.org/revolution/memory-storage/8 Memory & storage], Computer history museum

{{Basic computer components}}