nas

Network-attached storage (NAS) is the name given to dedicated data storage technology that can be connected directly to a computer network to provide centralized data access and storage to heterogeneous network clients.

Description

NAS differs from traditional file serving and Direct Attached Storage in that the operating system and other software on the NAS unit provides only the functionality of data storage, data access and the management of these functionalities. Furthermore, the NAS unit does not limit clients to only one file transfer protocol. NAS systems usually contain one or more hard disks, often arranged into logical, redundant storage containers or RAID arrays, as do traditional file servers. NAS removes the responsibility of file serving from other servers on the network and can be deployed via commercial embedded units or via standard computers running NAS software.

NAS uses file-based protocols such as NFS (popular on UNIX systems) or Common Internet File System (CIFS) (used with MS Windows systems). Contrast NAS's file-based approach and use of well-understood protocols with storage area network (SAN) which uses a block-based approach and generally runs over proprietary protocols. Minimal-functionality or stripped-down operating systems are used on NAS computers or devices which run the protocols and file applications that provide the NAS functionality. A "leaned-out" FreeBSD is used in FreeNAS, for example, which is open source NAS software meant to be deployed on standard computer hardware. Commercial embedded devices and consumer "network appliances" may use closed source operating systems and protocol implementations.

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. Auspex Systems was one of the first to develop a dedicated NFS server, following the 3Server's lead in the PC and MacIntosh worlds, eventually embedding both a PC and Sun server within their arrays. A group of Auspex engineers split away to create the integrated Network Appliance "filer", which supported both Windows and UNIX, in the early 1990s, starting the market for proprietary NAS arrays.

Benefits

Availability of data can potentially be increased with NAS because data access is not dependent on a server: the server can be down and users will still have access to data on the NAS. Performance can be increased by NAS because the file serving is done by the NAS and not done by a server responsibile for also doing other processing. The performance of NAS devices, though, depends heavily on the speed of and traffic on the network and on the amount of cache memory (the equivalent of RAM) on the NAS computers or devices. Scalability of NAS is not limited by the number of internal or external IO interfaces of a server as a NAS device can be connected to any available network jack. NAS can be more reliable than DAS because all the other things that can bring a server down do not affect the NAS device dedicated to file serving.

NAS applications

NAS is useful for more than just general centralized storage provided to client computers in environments with large amounts of data. NAS can enable simpler and lower cost systems such as load-balancing and fault-tolerant email and web server systems by providing storage services. The potential emerging market for NAS is the consumer market where there is a large amount of multi-media data. The price of NAS appliances has plummeted in recent years, offering flexible network based storage to the home consumer market for little more than the cost of a regular USB or FireWire external hard disk. Many of these home consumer devices are built around Processors running an Embedded Linux Operating system.^{citation needed]}

NAS is becoming popular for home and small business use. Small-footprint appliances that excel at low-power, low-noise, and low-cost are available from commercial vendors. Free NAS servers are also available to download from the internet, and include FreeNas, NASLite and Openfiler. They are easy to configure via a Web-based Interface and run on even the slowest computers.

Enterprise NAS Vendors

Appliance-based NAS was pioneered by Auspex, based on the success of file servers from Novell, IBM, Microsoft, and Sun Microsystems.

Current vendors include:

• Agámi Systems
• Attune Systems
• BlueArc, www
• EMC
• Isilon
• Network Appliance
• ONStor
• Panasas
• Pillar Data Systems

External links

• FreeNas
• Hitachi Data Systems
• FreeNas(Chinese)
• NASLite
• Openfiler
• Sun Microsystems - Productos Sun StorageTek
• EMC NAS
• [1]

See also

• Secure Shell Filesystem - locally mount a remote directory on a server using only a secure shell login.
• File Area Network
• Disk enclosure