Network attached storage (NAS)

Sunday, 19 November 2006

Network attached storage (NAS) is a storage system used to storage elements or devices that connect to a network and provide file access services to computer systems. A fundamental advantage of a computer network is that one computer system can write data to or read data from a memory device associated with another computer system within the network. A conventional information processing system stores information in a storage directly connected to a computer system. An access to information stored in the storage is permitted only through the use of the directly connected computer. Recently the development of network technologies and a dramatic increase in the amount of information to be stored promote separation of a computer system for processing information and a storage system for storing information. Storage can be connected to the network and has become capable of being shared by a plurality of computer systems. Such networked storage is referred to as a network storage. The flexibility offered by networked storage devices has changed the manner in which server networks are implemented. The explosive growth of networked computer systems and the large volume of data have created a need for a storage system that can support the bandwidth used and transfer rate required by computers and computer networks, and that can scale to support future increases in storage capacity. This need has stressed the capabilities of the traditional storage server model and has promoted the use of storage area network architectures, such as storage area network (SAN) and networked-attached storage (NAS). Storage area network (SAN) is a dedicated network that allows a few servers to share many high-speed storage systems. SAN allows a large storage system to be logically partitioned, with each partition attached to a server. Storage area networks (SANs) are dedicated networks that connect one or more hosts or servers to storage devices and subsystems. SANs may utilize a storage appliance to provide for management of the SAN. Network-attached storage (NAS) refers to self-contained disk storage systems that can be coupled directly to a network using an Ethernet cable in the same manner that a workstation is connected. They operate independently of any server and provide one or more disks packaged in a standalone enclosure. NAS devices generally transfer data files to and from other file servers or clients, whereas device level blocks of data may be transferred over a SAN. Network-attached storage (NAS) and storage area network (SAN) technologies are used to provide storage with greater capacity, higher reliability, and higher availability.

A network attached storage (NAS) device is a self-contained, intelligent storage appliance that attaches directly to a local area network (LAN) and transfers data typically over network standard protocols such as transmission control protocol/internet protocol (TCP/IP) or internet packet exchange (IPX), and using industry standard file sharing protocols such as server message block (SMB), common internet file system (CIFS), network file system (NFS), network control protocol (NCP), apple file protocol AFP, or hypertext transfer protocol (HTTP). The network attached storage is arranged to connect a plurality of storage device systems with the information processing apparatus through the network configured according to the TCP/IP so that the access to the storage device system may be realized on the file basis. Each NAS device is associated with a unique Internet Protocol (IP) address on the network. IP provides the basic communication protocol for a wide variety of computer networks including the Internet. A NAS device typically consists of an engine, which implements the file access services, and one or more storage devices, on which data is stored. A computer host system that accesses NAS devices uses a file system device driver to access the stored data. The file system device driver typically uses file access protocols such as NFS or CIFS. The NAS device having a file-system function is connected with the storage device system, so that the information processing apparatus may access to the storage device system on the file basis. NAS devices interpret these commands and perform the internal file and device input/output (I/O) operations necessary to execute them. In the network attached storage system, a dedicated server that provides file service via a network is provided on a disk array such that storage apparatuses can be directly accessed from the network. The file level access from the information processing apparatuses is allowed because the storage system is coupled to an apparatus having a file system function. The NAS system is equally accessible from any computing device on the network thereby greatly increasing the ability to scale and optimize the storage needs of the network. NAS devices allow the decomposition of server networks to storage-only components and diskless server components. This decomposition offers tremendous advantages to system administrators, including ease of deployment, system management, and enhanced scalability and reliability.

A typical NAS system involves several client computers and a dedicated file server attached via a local area network (LAN). NAS couples a plurality of storage systems managed in a RAID (redundant arrays of inexpensive disks) and information processing apparatuses through a network using TCP/IP to implement file level access to the storage systems. RAID is a method of creating one or more pools of data storage space from several hard drives. RAID combines multiple hard drives in a system, thus ensuring availability of data even if one or more hard drives fail. The function of a NAS system is to increase the overall performance of the system while reducing the total cost of ownership (TCO). The deployment of the NAS equipment provides advantages of the capability of centralized management of data, shared storage among a number of client computers, separate storage from an application server, and higher reliability and higher accessing speeds than hard disks that are employed by personal computers. The NAS system is independent of an operating system of the client computers, enabling the file server to be shared by heterogeneous client computers and application servers. This approach is also scalable and accessible, enabling additional storage to be easily added without disrupting the rest of the network or application servers. Network-attached storage (NAS) provides a solution to improve scalability of existing distributed file systems by removing the server as a bottleneck in using the network as bandwidth to allow parallelism by using striping and more efficient data pass. Network-attached storage offers convenient placement of storage devices. New functionality, such as the appearance of infinite disk capacity and plug-and-play configuration, can be incorporated. Improved performance and functionality at a reduced TCO are made possible by the ever increasing disk and switch device capabilities. An NAS system typically has a backup system for data recorded in a storage apparatus to periodically copy and preserve the data so that lost data can be recovered in the event there is a breakdown of an apparatus, and defect in a software, or when data is lost through erroneous operation.

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