Editing Network-attached storage (section)

== Description ==
A NAS unit is a computer connected to a network that provides only file-based data storage services to other devices on the network. Although it may technically be possible to run other software on a NAS unit, it is usually not designed to be a general-purpose server. For example, NAS units usually do not have a keyboard or display, and are controlled and configured over the network, often using a browser.<ref>{{cite magazine|title=An introduction to network attached storage|magazine=HWM Singapore|date=July 2003|issn=0219-5607|publisher=SPH Magazines|pages=90–92}}</ref>

A full-featured operating system is not needed on a NAS device, so often a stripped-down operating system is used.

NAS systems contain one or more hard disk drives, often arranged into logical, redundant storage containers or [[RAID]].

NAS uses file-based protocols such as [[Network File System (protocol)|NFS]] (popular on [[UNIX]] systems), SMB ([[Server Message Block]]) (used with [[Microsoft Windows]] systems), [[Apple Filing Protocol|AFP]] (used with [[Macintosh|Apple Macintosh]] computers), or NCP (used with [[Novell Open Enterprise Server|OES]] and [[NetWare|Novell NetWare]]). NAS units rarely limit clients to a single protocol.

=== Comparing with DAS ===
The key difference between [[direct-attached storage]] (DAS) and NAS is that DAS is simply an extension to an existing server and is not necessarily networked. As the name suggests, DAS typically is connected via a [[USB]] or [[Thunderbolt (interface)|Thunderbolt]] enabled cable. NAS is designed as an easy and self-contained solution for sharing files over the network.

Both DAS and NAS can potentially increase availability of data by using [[RAID]] or [[Computer cluster|clustering]].

Both NAS and DAS can have various amount of [[Cache (computing)|cache memory]], which greatly affects performance. When comparing use of NAS with use of local (non-networked) DAS, the performance of NAS depends mainly on the speed of and congestion on the network.

Most NAS solutions will include the option to install a wide array of software applications to allow better configuration of the system or to include other capabilities outside of storage (like video surveillance, virtualization, media, etc). DAS typically is focused solely on data storage but capabilities can be available based on specific vendor options.

=== Comparing with SAN ===
[[File:SANvsNAS.svg|thumb|Visual differentiation of NAS and [[storage area network|SAN]] use in network architecture]]
NAS provides both storage and a [[file system]]. This is often contrasted with SAN ([[storage area network]]), which provides only block-based storage and leaves file system concerns on the "client" side. SAN protocols include [[Fibre Channel]], [[iSCSI]], [[ATA over Ethernet]] (AoE) and [[HyperSCSI]].

One way to loosely conceptualize the difference between a NAS and a SAN is that NAS appears to the client OS (operating system) as a [[file server]] (the client can [[drive mapping|map]] network drives to shares on that server) whereas a disk available through a SAN still appears to the client OS as a disk, visible in disk and volume management utilities (along with client's local disks), and available to be formatted with a file system and [[Mount (computing)|mounted]].

Despite their differences, SAN and NAS are not mutually exclusive and may be combined as a SAN-NAS hybrid, offering both file-level protocols (NAS) and block-level protocols (SAN) from the same system{{citation_needed|date=May 2025}}. A [[shared disk file system]] can also be run on top of a SAN to provide filesystem services.