Editing USB (section)

=== USB mass storage / USB drive <span class="anchor" id="MASSSTORAGE"></span>===
{{See also|USB mass storage device class|Disk enclosure|External hard disk drive}}
[[File:SanDisk-Cruzer-USB-4GB-ThumbDrive.jpg|thumb|A [[USB flash drive|flash drive]], a typical USB mass-storage device]]
[[File:M.2 2242 SSD connected into USB 3.0 adapter.jpg|thumb|An [[M.2]] (2242) solid-state-drive ([[SSD]]) connected into a USB 3.0 adapter connected to computer]]

The [[USB mass storage device class]] (MSC or UMS) standardizes connections to storage devices. At first intended for magnetic and optical drives, it has been extended to support [[USB flash drive|flash drives]] and [[SD card]] readers. The ability to boot a write-locked [[SD card]] with a USB adapter is particularly advantageous for maintaining the integrity and non-corruptible, pristine state of the booting medium.

Though most personal computers since early 2005 can boot from USB mass storage devices, USB is not intended as a primary bus for a computer's internal storage. However, USB has the advantage of allowing [[hot-swapping]], making it useful for mobile peripherals, including drives of various kinds.

Several manufacturers offer external portable USB [[hard disk drive]]s, or empty enclosures for disk drives. These offer performance comparable to internal drives, limited by the number and types of attached USB devices, and by the upper limit of the USB interface. Other competing standards for external drive connectivity include [[eSATA]], [[ExpressCard]], [[FireWire]] (IEEE 1394), and most recently [[Thunderbolt (interface)|Thunderbolt]].

Another use for USB mass storage devices is the portable execution of software applications (such as web browsers and VoIP clients) with no need to install them on the host computer.<ref>{{cite web | url = http://www.makeuseof.com/tag/portable-software-usb/ | title = 100 Portable Apps for your USB Stick (both for Mac and Win) | access-date = 30 October 2008 | url-status=live | archive-url = https://web.archive.org/web/20081202121455/http://www.makeuseof.com/tag/portable-software-usb/ | archive-date = 2 December 2008}}</ref><ref>{{cite web | url = http://www.VoIP-Download.com/Skype.htm#USB/ | title = Skype VoIP USB Installation Guide | access-date = 30 October 2008 | url-status=dead | archive-url = https://web.archive.org/web/20140706153501/http://www.voip-download.com/Skype.htm#USB/ | archive-date = 6 July 2014}}</ref>