Network-attached storage (NAS) is file-level computer data storage connected to a computer network providing data access to heterogeneous network clients.

History

Network-attached storage was introduced with the early file sharing Novell's NetWare server operating system and NCP protocol in 1983. In the UNIX world, Sun Microsystems' 1984 release of NFS allowed network servers to share their storage space with networked clients. 3Com's 3Server and 3+Share software was the first purpose-built servers (including proprietary hardware, software, and multiple disks) for open systems servers, and the company led the segment from 1985 through the early 1990s. 3Com and Microsoft would develop the LAN Manager software and protocol to further this new market. Inspired by the success of file servers from Novell, IBM, and Sun, several firms developed dedicated file servers. While 3server was among the first firms to build a dedicated NAS for desktop operating systems, Auspex Systems was one of the first to develop a dedicated NFS server for use in the UNIX market. A group of Auspex engineers split away in the early 1990s to create the integrated NetApp filer, which supported both Windows' CIFS and UNIX'es NFS, and had superior scalability and ease of deployment. This started the market for proprietary NAS devices now led by NetApp and EMC Celerra.

Starting in the early 2000s, a series of startups emerged offering alternative solutions to single filer solutions in the form of clustered NAS – Spinnaker Networks (now acquired by NetApp), Exanet, IBRIX, Isilon, PolyServe (acquired by Hewlett-Packard in 2007), to name a few.

Description

A NAS unit is essentially a self-contained computer connected to a network, with the sole purpose of supplying file-based data storage services to other devices on the network. The operating system and other software on the NAS unit provide the functionality of data storage, file systems, and access to files, and the management of these functionalities. The unit is not designed to carry out general-purpose computing tasks, although it may technically be possible to run other software on it. NAS units usually do not have a keyboard or display, and are controlled and configured over the network, often by connecting a browser to their network address. The alternative to NAS storage on a network is to use a computer as a file server. In its most basic form a dedicated file server is no more than a NAS unit with keyboard and display and an operating system which, while optimised for providing storage services, can run other tasks; however, file servers are increasingly used to supply other functionality, such as supplying database services, email services, and so on.

A general-purpose operating system is not needed on a NAS device, and often minimal-functionality or stripped-down operating systems are used. For example FreeNAS, which is open source NAS software designed for use on standard computer hardware, is just a version of FreeBSD with all functionality not related to data storage stripped out. NASLite as the name suggests is a highly optimized version of Linux running from a floppy disk for the sole purpose of a NAS. Likewise, NexentaStor is based upon the core of the NexentaOS, an open source hybrid operating system with an OpenSolaris core and a GNU user environment.