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ABSTRACT
Information Technology (IT) departments are looking for cost-effective storage solutions that can offer performance, scalability, and reliability. As users on the network increase and the amounts of data generated multiply, the need for an optimized storage solution becomes essential. Network Attached Storage (NAS) is becoming a critical technology in this environment. The benefit of NAS over the older Direct Attached Storage (DAS) technology is that it separates servers and storage, resulting in reduced costs and easier implementation. As the name implies, NAS attaches directly to the LAN, providing direct access to the file system and disk storage. Unlike DAS, the application layer no longer resides on the NAS platform, but on the client itself. This frees the NAS processor from functions that would ultimately slow down its ability to provide fast responses to data requests. In addition, this architecture gives NAS the ability to service both Network File System (NFS) and Common Internet File System (CIFS) clients. Also this allows the IT manager to provide a single shared storage solution that can simultaneously support both Windows*-and UNIX*-based clients and servers. In fact, a NAS system equipped with the right file system software can support clients based on any operating system.
CONTENTS
1. HISTORY OF NETWORK ATTACHED STORAGE ¦¦¦¦¦¦¦¦.. 3
1.1 INTRODUCTION
1.2 BACKGROUND
2. STORAGE TOPOLOGIES ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦.. 5
2.1 TYPES OF STORAGE TOPOLOGIES
2.2 ADVANTAGES OF INTELLIGENT STORAGE
2.3 DIRECT ATTACHED STORAGE [DAS]
2.4 STORAGE AREA NETWORK [SAN]
2.5 NETWORK ATTACHED STORAGE [NAS]
3. COMPARISON BETWEEN STORAGE SYSTEMS ¦¦¦¦¦¦¦¦.. 10
3.1 NAS vs. TRADITIONAL FILE SERVERS OR DAS
3.2 NAS vs. SAN
3.3 NETWORK STORAGE RECAP
4. NAS DESCRIPTION ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦... 14
4.1 What Is NAS
4.2 DETAILED DESCRIPTION ON NAS
5. FURTHER TOPICS OF NAS ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦ 18
5.1 CONCEPT OF RAID
5.2 RAID LEVELS
5.3 NAS PROTOCOLS
5.4 NAS HEADS OR GATEWAYS
5.5 NAS BENEFITS, DRAWBACKS AND USES
6. CONCLUSION ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦. 25
7. REFERENCES ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦. 26
ACKNOWLEDGMENT
On presenting the report on Network Attached Storage, I feel greatly to express my humble feelings of thanks to one and all who have helped me directly or indirectly in the successful completion of the seminars.
I am grateful to my institution YELLAMMA DASAPPA Institute Of Technology and Department of Electronics & Communication and Engineering for imparting me the knowledge with which I can do my best.
I am grateful to Dr. K.V.S Ananda Babu, Principal, CMRIT, Bangalore for providing me congenial environment to work in.
I would like to thank my guide Prof. G Indumathi , HOD, Dept of ECE, who has helped me a lot in making this seminar report and for her continuous encouragement, guidance and moral support throughout the seminar work.

Finally, I would like to thank all Lecturers of Dept of ECE, all my friends, who with their constant and creative criticism, made me to maintain standards throughout my endeavor to complete this seminar work.
1. HISTORY OF NETWORK ATTACHED STORAGE
1.1 INTRODUCTION
You can never have enough storage, whether a bigger house to store your belongings or more hard disk space to store your data on a network. However dedicated network devices provide affordable, easy access to data. Several new methods of utilizing computer networks for data storage have emerged in recent years. One popular approach, Network Attached Storage (NAS), allows homes and businesses to store and retrieve large amounts of data more affordably than ever before.
1.2 BACKGROUND

Historically, floppy drives have been widely used to share data files, but today the storage needs of the average person far exceed the capacity of floppies. Businesses now maintain an increasingly large number of electronic documents and presentation sets including video clips. Home computer users, with the advent of MP3 music files and JPEG images scanned from photographs, likewise require greater and more convenient storage.

Central file servers use basic client/server networking technologies to solve these data storage problems. In its simplest form, a file server consists of PC or workstation hardware running a network operating system (NOS) that supports controlled file sharing (such as Novell NetWare, UNIX or Microsoft Windows). Hard drives installed in the server provide gigabytes of space per disk, and tape drives attached to these servers can extend this capacity even further.
File servers boast a long track record of success, but many homes, workgroups and small businesses cannot justify dedicating a fully general-purpose computer to relatively simple data storage tasks. So, 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, 3Servers 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.
STORAGE TOPOLOGIES
2.1 TYPES OF STORAGE TOPOLOGIES
Direct Attached Storage [DAS].
Storage Area Network [SAN].
Network Attached Storage [NAS].
2.2 ADVANTAGES OF INTELLIGENT STORAGE
Cost of Bandwidth
Cost of Space
Cost of Storage System v. Cost of Disks
Physical Repair, Number of Spare Parts
Cost of Processor Complexity
Cluster advantages: dependability, scalability
2.3 DIRECT ATTACHED STORAGE [DAS]
The most basic method of attaching storage to a network is a one-to-one direct connection to a network server. Disk arrays are typically connected to a server using SCSI connectors and then shared out to network users. Although this method is certainly the easiest to implement, it does not scale very gracefully as storage needs grow. As a DAS system grows it becomes exponentially unwidely, costly to backup. manage and maintain and unreliable. Additionally, administration of DAS can become more difficult with the potential proliferation of disparate systems.
DIRECT ATTACHED STORAGE (DAS) TOPOLOGY
2.4 STORAGE AREA NETWORK [SAN]

A SAN is a network of storage devices that are connected to each other and to a server, or cluster of servers, which act as an access point to the SAN. In some configurations a SAN is also connected to the network. SAN's use special switches as a mechanism to connect the devices. These switches, which look a lot like a normal Ethernet networking switch, act as the connectivity point for SAN's. Making it possible for devices to communicate with each other on a separate network brings with it many advantages. Consider, for instance, the ability to back up every piece of data on your network without having to 'pollute' the standard network infrastructure with gigabytes of data. This is just one of the advantages of a SAN which is making it a popular choice now a days.
Storage Area Network (SAN) Topology
2.5 NETWORK ATTACHED STORAGE [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.
A typical NAS solution, where all traffic flows over the production LAN.
Network-attached storage (NAS) is hard disk storage that is set up with its own network address rather than being attached to the department computer that is serving applications to a network's workstation users. By removing storage access and its management from the department server, both application programming and files can be served faster because they are not competing for the same processor resources. The network-attached storage device is attached to a local area network (typically, an Ethernet network) and assigned an IP address. File requests are mapped by the main server to the NAS file server.
The growing market for network storage is a result of the exploding demand for storage capacity in our increasingly internet-dependent world and its tight labor market. Storage area networks (SAN) and network attached storage (NAS) are two proven approaches to networking storage technically including a file system in a storage subsystem differentiates NAS which has one from SAN, which doesnâ„¢t in practice, however it is often NASâ„¢ s close association with ethernet hardware
3. COMPARISON BETWEEN STORAGE SYSTEMS
3.1 NAS vs. TRADITIONAL FILE SERVERS OR DAS
Proponents of NAS claim that NAS technology provides these advantages over traditional file servers:
Lower cost
Better Security
Higher Availability (less downtime)
Easier to use and administer
NAS differs from the traditional file serving and Direct Attached Storage in that the operating system and other software on the NAS unit provide 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 RAIDs(redundant arrays of independent disks), 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 products improve on traditional file servers generally through the principle of simplification. By stripping out all of the unnecessary capabilities of a general purpose server -applications, services or daemons, and hardware peripherals -a NAS device becomes less prone to system "crashes" and security attacks. When a problem does occur, a NAS system can be diagnosed and rebooted much faster due to its lower level of complexity.
NAS products also generally hide the operating system personality of the device. Whereas Windows, UNIX and NetWare file servers each demand specific protocol support on the client side, NAS systems strive for greater operating system independence of clients.

Opponents of NAS emphasize that traditional file servers have a proven record of success compared to this new breed of "upstart" NAS systems. High-end file systems also contain more processing power than a NAS device, giving servers a performance edge (in terms of transactions or I/O per second rates) over NAS.

The new breed of NAS networking products has succeeded in providing a reasonable alternative to traditional file servers in client/server networks. Entry-level NAS products containing 20-50 gigabytes of storage can be purchased for $500 (USD) or less, whereas mid-range and high-end NAS systems can run in the tens of thousands of dollars. Besides cost, a NAS promises reliable operation and easy management.
3.2 NAS vs. SAN
At a high level, Storage Area Networks (SAN s) serve the same purpose as a NAS system. A SAN supplies data storage capability to other network devices. Traditional SAN s differed from traditional NAS in several ways. Specifically, SAN s often utilized Fibre Channel rather than Ethernet, and a SAN often incorporated multiple network devices or "endpoints" on a self-contained or "private" LAN, whereas NAS relied on individual devices connected directly to the existing public LAN. The traditional NAS system is a simpler network storage solution, effectively a subset of a full SAN implementation.

The distinction between NAS and SAN has grown fuzzy in recent times, as technology companies continue to invent and market new network storage products. Today's SAN s sometimes use Ethernet, NAS systems sometimes use Fibre Channel, and NAS systems sometimes incorporate private networks with multiple endpoints. Fibre Channel is a technology used to interconnect storage devices allowing them to communicate at very high speeds (up to 10Gbps in future implementations).The primary differentiator between NAS and SAN products now boils down to the choice of network protocol. SAN systems transfer data over the network in the form of disk blocks (fixed-sized file chunks, using low-level storage protocols like SCSI) whereas NAS systems operate at a higher level with the file itself.
3.3 NETWORK STORAGE RECAP

Storage area network

Network attached storage
Connectivity
Fibre Channel, iSCSI
IP
Data access method
Block
File
Key requirement Deterministic performance, support for high-transaction applications
Sharing, collaboration
Type of applications
OLTP, data warehousing, ERP, SCM, etc
File and print server consolidation, product design, engineering
Typical market segment
Large businesses, midsize, SMBs “ iSCSI
All
4. NAS DESCRIPTION
4.1 What Is NAS
NAS challenges the traditional file server approach by creating systems designed specifically for data storage. Instead of starting with a general-purpose computer and configuring or removing features from that base, NAS designs begin with the bare-bones components necessary to support file transfers and add features "from the bottom up."
General structure of Network Attached Storage [NAS].
Like traditional file servers, NAS follows a client/server design. A single hardware device, often called the NAS box or NAS head, acts as the interface between the NAS and network clients. These NAS devices require no monitor, keyboard or mouse. They generally run an embedded operating system rather than a full-featured NOS. One or more disk (and possibly tape) drives can be attached to many NAS systems to increase total capacity. Clients always connect to the NAS head, however, rather than to the individual storage devices. Clients generally access a NAS over an Ethernet connection. The NAS appears on the network as a single "node" that is the IP address of the head device.
A NAS can store any data that appears in the form of files, such as email boxes, Web content, remote system backups, and so on. Overall, the uses of a NAS parallel those of traditional file servers. NAS systems strive for reliable operation and easy administration. They often include built-in features such as disk space quotas, secure authentication, or the automatic sending of email alerts should an error be detected. The advantage of NAS is that it concentrates on managing the file requests and storage; it is not sharing processor power with applications and general users. This also means that it is faster to reboot if problems occur. Because Network speeds are now as fast as internal server processing, NAS is as fast as DAS.
4.2 DETAILED DESCRIPTION ON NAS
Network Attached Storage, or NAS, is a data storage mechanism that uses special devices connected directly to the network media. These devices are assigned an IP address and can then be accessed by clients via a server that acts as a gateway to the data, or in some cases allows the device to be accessed directly by the clients without an intermediary.

The beauty of the NAS structure is that it means that in an environment with many servers running different operating systems, storage of data can be centralized, as can the security, management, and backup of the data. An increasing number of companies already make use of NAS technology, if only with devices such as CD-ROM towers (stand-alone boxes that contain multiple CD-ROM drives) that are connected directly to the network).
Some of the big advantages of NAS include the expandability; need more storage space, add another NAS device and expand the available storage. NAS also bring an extra level of fault tolerance to the network. In a DAS environment, a server going down means that the data that that server holds is no longer available. With NAS, the data is still available on the network and accessible by clients. Fault tolerant measures such as RAID, can be used to make sure that the NAS device does not become a point of failure.
Generally NAS are used, in order the high up would wind at installation and administration of a dedicated file server to go around. A NAS is usually to install simply, easily scalable, to administrater simply. Since the functions with the targeted application to be very specifically co-ordinated can. In this way error causes are avoided from the beginning e.g. due to more extensive and for the special targeted application than NAS of unnecessary configuration options. File-based services such as NFS or SMB/CIFS represent the kernel function. Therefore NAS systems are called Filer often briefly.
Network-attached storage consists of hard disk storage, including multi-disk RAID systems, and software for configuring and mapping file locations to the network-attached device. Network-attached storage can be a step toward and included as part of a more sophisticated storage system known as a storage area network.

NAS software can usually handle a number of network protocols, including Microsoftâ„¢ s Internetwork Packet exchange and NetBEUI, Novell's Netware Internetwork Packet exchange, and Sun Microsystemsâ„¢ Network File System. Configuration, including the setting of user access priorities, is usually possible using a Web browser. A NAS can have either own fixed disk (NAS Appliance) or to a Storage Area network (SAN) be attached (NAS head, NAS head) and over it memory of attached storage systems to use.
A network-attached storage (NAS) device is a server that is dedicated to nothing more than file sharing. NAS does not provide any of the activities that a server in a server-centric system typically provides, such as e-mail, authentication or file management. NAS allows more hard disk storage space to be added to a network that already utilizes servers without shutting them down for maintenance and upgrades. With a NAS device, storage is not an integral part of the server. Instead, in this storage-centric design, the server still handles all of the processing of data but a NAS device delivers the data to the user. A NAS device does not need to be located within the server but can exist anywhere in a LAN and can be made up of multiple networked NAS devices.
NAS uses file-based protocols such as NFS (popular on UNIX systems) or SMB (Server Message Block) 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 SCSI over Fibre Channnel or iSCSI (There are other SAN protocols as well, such as ATA over ethernet and HyperSCSI, which however are less common.
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.

Network-attached storage is one way around the slowdowns and service interruptions that occur in a conventional file server model.
5.FURTHER TOPICS OF NAS
5.1 CONCEPT OF RAID
DEFINITION: Redundant Array of Independent Disks [RAID], A disk subsystem that is used to increase performance or provide fault tolerance or both. RAID uses two or more ordinary hard disks and a RAID disk controller. In the past, RAID has also been implemented via software only.
Small and Large RAID subsystems come in all sizes from desktop units to floor-standing models. Stand-alone units may include large amounts of cache as well as redundant power supplies. Initially used with servers, desktop PCs are increasingly being retrofitted by adding a RAID controller and extra IDE or SCSI disks. Newer motherboards often have RAID controllers.Disk Striping
RAID improves performance by disk striping, which interleaves bytes or groups of bytes across multiple drives, so more than one disk is reading and writing simultaneously.
Mirroring and Parity
Fault tolerance is achieved by mirroring or parity. Mirroring is 100% duplication of the data on two drives (RAID 1). Parity is used to calculate the data in two drives and store the results on a third (RAID 3 or 5). After a failed drive is replaced, the RAID controller automatically rebuilds the lost data from the other two. RAID systems may have a spare drive (hot spare) ready and waiting to be the replacement for a drive that fails. The parity calculation is performed in the following manner: a bit from drive 1 is XOR' d with a bit from drive 2, and the result bit is stored on drive 3 (see OR for an explanation of XOR).
5.2 RAID LEVELS
RAID 0 - Speed (Widely Used)
RAID level 0 is disk striping only, which interleaves data across multiple disks for performance. Widely used for gaming, RAID 0 has no safeguards against failure.
RAID 1 - Fault Tolerance (Widely Used)
Uses disk mirroring, which provides 100% duplication of data. Offers highest reliability, but doubles storage cost. RAID 1 is widely used in business applications.
RAID 2 - Speed
Instead of single bytes or groups of bytes (blocks), bits are interleaved (striped) across many disks. The Connection Machine used this technique, but this is rarely used because 39 disks are required.
RAID 3 - Speed and Fault Tolerance
Data are striped across three or more drives. Used to achieve the highest data transfer, because all drives operate in parallel. Using byte level striping, parity bits are stored on separate, dedicated drives.
RAID 4 - Speed and Fault Tolerance
Similar to RAID 3, but uses block level striping. Not often used.
RAID 5 - Speed and Fault Tolerance (Widely Used)
Data are striped across three or more drives for performance, and parity bits are used for fault tolerance. The parity bits from two drives are stored on a third drive and are interspersed with user data. RAID 5 is widely used in servers.
RAID 6 - Speed and Fault Tolerance
Highest reliability because it can recover from a failure of two disks, but not widely used. Similar to RAID 5, but performs two different parity computations or the same computation on overlapping subsets of the data.
RAID 10, RAID 100 - Speed and Fault Tolerance
RAID 10 is RAID 1 + 0. The drives are striped for performance (RAID 0), and all striped drives are duplicated (RAID 1) for fault tolerance.RAID 100 is RAID 10 + 0. It adds a layer of striping on top of two or more RAID 10 configurations for even more speed.
5.3 NAS PROTOCOLS
Communication with a NAS head occurs over TCP/IP. More specifically, clients utilize any of several higher-level protocols (application or layer seven protocols in the OSI model) built on top of TCP/IP.
The two application protocols most commonly associated with NAS are Sun Network File System (NFS) and Common Internet File System (CIFS). Both NFS and CIFS operate in client/server fashion. Both predate the modern NAS by many years; original work on these protocols took place in the 1980s.
Many NAS systems also support Hypertext Transfer Protocol (HTTP). Clients can often download files in their Web browser from a NAS that supports HTTP. NAS systems also commonly employ HTTP as an access protocol for Web-based administrative user interfaces.
5.4 NAS HEADS OR GATEWAYS
The hardware that performs the NAS control functions is called a NAS head or NAS gateway. The clients always connect to the NAS head, as it is the NAS head is addressable on the network. A NAS head is usually a discrete hardware device that is independent of the storage devices and contains an imbedded operating system that does not need a keyboard, mouse or monitor. A storage administrator accesses the appliance and manages the disk resources from a remote console. Disks and in some cases tape drives are attached to the NAS head for capacity. NAS Heads are also sometimes called NAS appliances, based on the ideas that NAS is a commodity item like a toaster or washing machine.
A NAS head may also 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
5.5 NAS BENEFITS
Storing Unstructured data: Network Attached Storage is a more appropriate solution for storing and managing unstructured type of data, from a cost and usability perspective. NAS appears to the user as a normal network drive or server, but in fact it can be centralized and store many terabytes of data.
Computer Network support: The NAS Server comes network ready and connects to your Ethernet hub. It's truly plug-and-play. The Server networks and manages hard disks on Windows NT/200/2003, Apple and UNIX networks concurrently. It simultaneously supports multiple protocols. The NAS8200 systems come with dual Gigabit Ethernet interfaces and the NAS8100 systems have optional Gb Ethernet interfaces to the network.
RAID Data Protection: The NAS Server supports RAID 0 (Striping), RAID 1 (Mirroring) and RAID 5. The NAS system supports hot-swap EIDE drives.
Storage/application host independence: Multiple application servers and/or clients can directly access needed information. This yields a high degree of flexibility, without having to rearrange hardware.
The appliance approach: The storage server can be streamlined and optimized to do one thing - serving data - very well.
Leveraging existing Expertise: since it uses standard technologies that users are already familiar with, along with their existing infrastructure).
Easy Seamless Sharing: The NAS Server operates with unmatched simplicity right out of the carton. The server appears in the network neighborhood and can be mapped to a single drive letter. This is an independent network appliance, its operation neither affects nor is impacted by the network file server. The NAS Server appears as a server on your network, and can be accessed as such. Hundreds of users can simultaneously access the hard drives with unmatched ease and simplicity.
Easy to install and manage: Installation is very easy. Just plug in the Ethernet cable, plug in the power cable and turn on the unit. There's no software to load. A quick installation wizard, and a Web Browser are used to configure the NAS Server. It allows you to set up security by individual and group. Your server is never out of date - you can download the latest firmware as it becomes available.
Built to user requirements: We will configure a system to your requirements. Select - capacity, tower or rack cabinet, EIDE drives, RAID or just plain drives, hot-swap drives, hot-swap power.
Other Benefits: NAS helps improve the performance of your file stores and ensures that users continue to have reliable access to their files for as long as necessary. This in turn helps to enhance user satisfaction and boost productivity. 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.
DRAWBACKS
Due to the multiprotocol, and the reduced CPU and OS layer, the NAS has its limitations compared to the DAS/SAN 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.
Certain NAS devices 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 mirror efficiently with rsync. One may still use rsync, but through an NFS or CIFS client; that method fails to enumerate huge file hierarchies at the nominal speed of local drives and induces considerable network traffic.
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.
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.
6.CONCLUSION
Storage systems are becoming the dominant investment in corporate data centers and a crucial asset in e-commerce, making the rate of growth of storage a strategic business problem and a major business opportunity for storage vendors. In order to satisfy user needs, storage systems should consolidate resources, deploy quickly, be centrally managed, be highly available, and allow data sharing. It should also be possible to distribute them over global distances, make them secure against external and internal abuse, and scale their performance with capacity. Putting storage in specialized systems and accessing it from clients across a network provides significant advantages for users. Moreover, the most apparent difference between the NAS and SAN versions of network storage”use of Ethernet in NAS and Fibre Channel in SAN”is not a core difference and may soon not even be a recognizable difference. Instead, we may have NAS servers that look like disks, disks that connect to and operate on Ethernet, arrays of disk bricks that, as far as the user is concerned, function as one big disk, and arrays of smart disks that verify every command against the rights of individual
users.
7.REFERENCES
1. http://wikipedia.com.
2. http://brocade.com.
3. http://storageadmin.com.
4. http://netapp.com.
5. http://perforce.com.

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