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Information about Network Attached Storage

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

Description

NAS hardware is similar to the traditional file server equipped with direct attached storage. However it differs considerably on the software side. 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. Use of NAS devices for other purposes (like scientific computations or running database engine) is strongly discouraged. Many vendors also purposely make it hard to develop or install any third-party software on their NAS device by using closed source operating systems and protocol implementations. In other words, NAS devices are server appliances.

NAS units also usually have a web interface as opposed to monitor/keyboard/mouse.

Often minimal-functionality or stripped-down operating systems are used on NAS devices. For example FreeNAS, which is open source NAS software meant to be deployed on standard computer hardware, is in fact a "leaned-out" version of FreeBSD.

NAS systems usually contain one or more hard disks, often arranged into logical, redundant storage containers or RAIDs (redundant arrays of independent disks), as do traditional file servers. NAS removes the responsibility of file serving from other servers on the network.

NAS uses file-based protocols such as NFS (popular on UNIX systems) or SMB (Server Message Block) (used with MS Windows systems). NAS units rarely limit clients to only one protocol.

NAS provides both storage and filesystem. This is often contrasted with SAN (Storage Area Network), which provides only block-based storage and leaves filesystem concerns on the "client" side. SAN protocols are SCSI, Fibre Channel, iSCSI, ATA over Ethernet, or HyperSCSI.

The boundaries between NAS and SAN systems are also starting to overlap, with some products making the obvious next evolution and offering both file level protocols (NAS) and block level protocols (SAN) from the same system. However a SAN device is usually served through NAS as one large flat file, not as a filesystem per se. An example of this is Openfiler, a free product running on Linux.

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 to create the integrated Network Appliance "filer", which supported both Windows and UNIX, in the early 1990s, starting the market for proprietary NAS arrays. Starting in the early 2000s, a series of startups emerged offering alternative solutions to single filer solutions in the form of clustered NAS – Exanet, IBRIX, Isilon, PolyServe to name a few.

Benefits

Availability of data might potentially be increased with NAS if it provides built-in RAID and clustering.

Performance can be increased by NAS because the file serving is done by the NAS and not done by a server responsible 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 (RAM) on the NAS computers or devices.

It should be noted that NAS is effectively a server in itself, with all major components of a typical PC – a CPU, motherboard, RAM, etc. – and its reliability is a function of how well it is designed internally. A NAS without redundant data access paths, redundant controllers, redundant power supplies, is probably less reliable than Direct Attached Storage (DAS) connected to a server which does have redundancy for its major components.

Drawbacks

Due to the multiprotocol, and the reduced CPU and OS layer, the NAS has its limitations compared to the DAS/FC systems. If the NAS is occupied with too many users, too many I/O operations, or CPU processing power that is too demanding, the NAS reaches its limitations. A server system is easily upgraded by adding one or more servers into a cluster, so CPU power can be upgraded, while the NAS is limited to its own hardware, which is in most cases not upgradeable.

NAS will also fail to expose well-known services that are typical of a file server, or enable them in a way that is not efficient. Examples are: ability to compute disk usage of separate directories, ability to index files rapidly (locate), ability to mirrorize efficiently with rsync. You may still rsync, but through a NFS client; that method fails to enumerate huge file hierarchies at the nominal speed of local drives and induces important network traffic.

The key difference between DAS and NAS is that DAS is simply an extension to an existing server and is not networked while NAS sits on a network as its own entity; it is easier to share files with NAS. NAS typically has less CPU and I/O power compared to DAS.

NAS uses

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. Such consumer market appliances are now commonly available. Unlike their rackmounted counterparts, they are generally packaged in smaller form factors. 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 ARM, PowerPC or MIPS processors running an embedded Linux operating system. Examples include Buffalo's TeraStation [1] and Linksys NSLU2 [2]. More recently, home NAS devices have incorporated support for the Universal Plug and Play protocol, enabling them to serve the growing number of networked home media players.

NAS heads

A NAS head refers to a NAS which does not have any on-board storage, but instead connects to a SAN. In effect, it acts as a translator between the file-level NAS protocols (NFS,CIFS,etc.) and the block-level SAN protocols (Fibre Channel, iSCSI). Thus it can combine the advantages of both technologies. The term "NAS head" is sometimes also used to refer to the portion of a self-contained NAS system other than its storage. An example would be the ONStor Bobcat.

NAS operating systems for consumer PCs

Open source NAS-oriented distributions of Linux and FreeBSD are also available, including FreeNAS, NASLite and Openfiler. They are easy to configure via a Web-based Interface and run on low-end conventional computers. They can run from a LiveCD, bootable USB flash drive, or from one of the mounted hard drives. They run Samba, NFS daemon, and FTP daemons which are freely available for those operating systems.

See also

Computer data storage, computer memory, and often casually storage or memory refer to computer components, devices and recording media that retain digital data used for computing for some interval of time.
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as a college campus, industrial complex, or a military base. A CAN, may be considered a type of MAN (metropolitan area network), but is generally limited to an area that is smaller than a typical MAN.
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In telecommunication, the term file server has the following meanings:
  • A form of disk storage that hosts files within a network; file servers do not need to be high-end but must have enough disk space to incorporate a large amount of data.

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Direct-attached storage (DAS) refers to a digital storage system directly attached to a server or workstation, without a storage network in between. It is a retronym, mainly used to differentiate non-networked storage from SAN and NAS.
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An operating system (OS) is the software that manages the sharing of the resources of a computer. An operating system processes system data and user input, and responds by allocating and managing tasks and internal system resources as a service to users and programs of the
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server appliance is a form of Internet appliance that is a computer server. They are designed so that the end user does not need to understand the workings of the operating system or of the commands associated with it.
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FreeNAS is a free NAS (Network-attached storage) server, supporting: CIFS (Samba), FTP, NFS, rsync, AFP protocols, S.M.A.R.T., local user authentication, and software RAID (0,1,5), with a web-based configuration interface.
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FreeBSD is a Unix-like free operating system descended from AT&T UNIX via the Berkeley Software Distribution (BSD) branch through the 386BSD and 4.4BSD operating systems.
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Raid or RAID may refer to:
  • Redundant Array of Independent/Inexpensive Disks, or RAID, a system of multiple hard drives for sharing or replicating data.

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For network file systems in general, see .


Network File System (NFS) is a network file system protocol originally developed by Sun Microsystems in 1984, allowing a user on a client computer to access files over a network as easily as if the network
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Unix (officially trademarked as UNIX®) is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs including Ken Thompson, Dennis Ritchie and Douglas McIlroy.
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Server Message Block (SMB) is an application-level network protocol mainly applied to shared access to files, printers, serial ports, and miscellaneous communications between nodes on a network. It also provides an authenticated Inter-process communication mechanism.
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In computing, a storage area network (SAN) is an architecture to attach remote computer storage devices (such as disk arrays, tape libraries and optical jukeboxes) to servers in such a way that, to the operating system, the devices appear as locally attached.
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SCSI (Small Computer System Interface) is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, and electrical and optical interfaces.
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Fibre Channel is a gigabit-speed network technology primarily used for storage networking. Fibre Channel is standardized in the T11 Technical Committee of the InterNational Committee for Information Technology Standards (INCITS), an American National Standards Institute
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Internet SCSI (iSCSI) is a network protocol standard, officially ratified on 2003-02-11 by the Internet Engineering Task Force, that allows the use of the SCSI protocol over TCP/IP networks. iSCSI is a transport layer protocol in the SCSI-3 specifications framework.
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ATA over Ethernet (AoE) is a network protocol developed by the Brantley Coile Company [1] , designed for accessing ATA storage devices over Ethernet networks. It gives the possibility to build SANs with low-cost, standard technologies.
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In computer science, HyperSCSI is a network protocol for sending and receiving SCSI commands. HyperSCSI is unlike iSCSI in that it bypasses the IP suite and works directly over Ethernet.
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Openfiler is an operating system that provides file-based network-attached storage and block-based Storage area network. It was created by Xinit Systems, and is based on the rPath Linux distribution. It is free software licensed under the GNU General Public License version 2.
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Novell Inc.

Public (NASDAQ:  NOVL )
Founded Provo, Utah (1983)
Headquarters Waltham, MA, USA

Key people Ron Hovsepian, CEO and President
John Dragoon, Senior Vice President, CMO
Dana Russell, Senior Vice President, CFO
Industry Software
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NetWare is a network operating system developed by Novell, Inc. It initially used cooperative multitasking to run various services on a PC, and the network protocols were based on the archetypal Xerox XNS stack.
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The NetWare Core Protocol (NCP) is a network protocol used in some products from Novell, Inc. It is usually associated with the NetWare operating system, but parts of it have been implemented on other platforms such as Linux, Windows NT and various flavors of Unix.
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Sun Microsystems

Public (NASDAQ:  JAVA )
Founded 1982
Headquarters Santa Clara, California, United States

Key people Scott McNealy, Chairman
Jonathan I.
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For network file systems in general, see .


Network File System (NFS) is a network file system protocol originally developed by Sun Microsystems in 1984, allowing a user on a client computer to access files over a network as easily as if the network
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3Com Corporation

Public NASDAQ:  COMS
Founded 1979
Headquarters Marlborough, Massachusetts, United States

Key people Edgar Masri, Pres. & CEO
Eric A. Benhamou, Chairman
Donald Halstead, III, CFO & Exec.
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The 3Com 3Server was a headless dedicated network server machine designed to run 3Com LAN server software.

The companion product was the diskless 3Station network workstation, a dedicated client machine.
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3+Share was a pioneering file and print sharing product from 3Com. Introduced in the early 1980s, 3+Share was competitive with Novell's NetWare in the open systems network server business throughout the 1980s.
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Microsoft Corporation

Public (NASDAQ:  MSFT )
Founded Albuquerque, New Mexico, USA (April 4 1975)[1]
Headquarters Redmond, Washington, United States

Key people Bill Gates, Co-founder and Executive Chairman ;
Paul Allen, Co-founder ;
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The LAN Manager (not to be confused with NTLM) was an advanced Network Operating System (NOS) from Microsoft developed in cooperation with 3Com. It was designed to succeed 3Com's innovative 3+Share network server software which ran on top of MS-DOS.
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In telecommunication, the term file server has the following meanings:
  • A form of disk storage that hosts files within a network; file servers do not need to be high-end but must have enough disk space to incorporate a large amount of data.

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