network attached storage

[computer science crazy]

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ABSTRACT
The incremental growth of the Internet for communications within and between companies has raised an important issue of where and how to store all the information being generated and to ensure it is safe and secure in the event of system crashes and other crises. As a result 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 technologies 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 older technologies, 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.

INTRODUCTION
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. As shown in the figure below, 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.
NAS is typically implemented as a network appliance, requiring a small form factor (both real estate and height) as well as ease of use. NAS is a solution that meets the ever-demanding needs of today's networked storage market.

NAS Appliance in a Local Area Network

NETWORK STORAGE CONCEPTS
In basic terms, network storage is simply about storing data using a method by which it can be made available to clients on the network. Over the years, the storage of data has evolved through various phases. This evolution has been driven partly by the changing ways in which we use technology, and in part by the exponential increase in the volume of data we need to store. It has also been driven by new technologies, which allow us to store and manage data in a more effective manner.
In the days of mainframes, data was stored physically separate from the actual processing unit, but was still only accessible through the processing units. As PC based servers became more commonplace, storage devices went 'inside the box' or in external boxes that were connected directly to the system. Each of these approaches was valid in its time, but as our need to store increasing volumes of data and our need to make it more accessible grew, other alternatives were needed. Enter network storage.
Network storage is a generic term used to describe network based data storage, but there are many technologies within it which all go to make the magic happen. Here is a rundown of some of the basic terminology that you might happen across when reading about network storage.
Direct Attached Storage (DAS)
Direct attached storage is the term used to describe a storage device that is directly attached to a host system. The simplest example of DAS is the internal hard drive of a server computer, though storage devices housed in an external box come under this banner as well. DAS is still, by far, the most common method of storing data for computer systems. Over the years, though, new technologies have emerged which work, if you'll excuse the pun, out of the box.
Network Attached Storage (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.

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 with companies today, and is a reason why it is forecast to become the data storage technology of choice in the coming years.

WHAT IS NETWORK ATTACHED STORAGE
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.
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.
Network Attached Storage separates the application server from the storage. This increases overall system performance by allowing the servers to perform application requests and the NAS to serve files or run applications.

NAS BLOCK DIAGRAM


FUNCTIONAL DESCRIPTION
Midrange NAS Architecture
The proposed platform in this section is a midrange NAS appliance. This type of platform is typically housed in a 1U rack and scales to several terabytes of storage across eight or more SCSI drives controlled by hardware-based RAID. Dual processors, fast PCI-X I/O, and fast DDR memory all contribute to system performance while redundant Gigabit Ethernet connections help reduce LAN bottlenecks.
Intel Pentium III processor with 512 KB L2 Cache: The Intel Pentium III processor with 512 KB L2 Cache is an excellent solution for NAS appliances. The Pentium III processor implements a Dynamic Execution micro architecture”a unique combination of multiple branch prediction, data flow analysis, and speculative execution. This enables the Pentium III processor to deliver higher performance while maintaining binary compatibility with all previous Intel Architecture processors. The processor also executes Intel® MMX„¢ technology instructions for enhanced media and communication performance. Additionally, the Pentium III processor executes Streaming Single-Instruction Multiple Data (SIMD) Extensions for enhanced floating-point performance. Data prefetch logic adds functionality that anticipates the data needed by the application and pre-loads it into the advanced transfer cache. The processor utilizes multiple low-power states to conserve power during idle times. The Pentium III processor is available in either a 478-pin FCPGA2 or a 479-ball micro FCBGA, and supports core frequencies ranging from 800 MHz to 1.26 GHz.
IOP321 I/O Processor: The IOP321 is a single function device that integrates a 600 MHz Intel® XScale„¢ core with intelligent peripherals including a PCI bus, which supports 133 MHz operation in PCI-X mode. Other integrated features include an address translation unit, messaging unit, DMA, peripheral bus interface unit, memory controller for PC200 DDR SDRAM, application accelerator unit, and I2C interface. The I/O processor offloads the RAID function from the host processor resulting in increased performance.
82546EB Dual Port Gigabit Ethernet Controller: The 82546EB integrates a dual 10/100/1000 Mbps MAC and PHY into a single 21 x 21 mm BGA package. The device is optimized for enterprise networking and server appliances that use PCI or PCI-X.
Processor System Bus (PSB): The Pentium III processor uses the original low voltage signaling of the Gunning Transceiver Logic (GTL) technology for the system bus. The GTL system bus operates at 1.25V signal levels vs. GTL+, which operates at 1.5V signal levels. This bus provides a 32-bit address bus with a 64-bit data bus at 133 MHz, resulting in a total bandwidth of 1 GB/s.
Double Data Rate (DDR) Memory Bus: The integrated memory controller provides a single 64-bit wide (72-bit for ECC) DDR memory channel supporting up to 8 GB of local memory. The address and control bus operates at 100 or 133 MHz. Data is acquired on the rising and falling edge of the clock doubling the data rate to 200 or 266 MHz, providing bandwidths of 1.6 GB/s and 2.1 GB/s respectively.
Peripheral Component Interconnect eXtended (PCI-X): PCI-X enables the design of systems and devices that operate at clock speeds up to 133 MHz, or 1 GB/s. The PCI-X protocol enhancements enable devices to operate much more efficiently, thereby providing more usable bandwidth at any clock frequency. PCI-X provides backward compatibility by allowing devices to operate at conventional PCI frequencies and modes when installed in conventional systems. The PCI-X bus provides a 64-bit data bus that is capable of running at 133 MHz with one device providing 1 GB/s bandwidth, 100 MHz with two devices providing 800 MB/s bandwidth, and 66 MHz with three or four devices providing 533 MB/s bandwidth.
Peripheral Component Interconnect (PCI): The PCI local bus is a high-performance 64-bit bus with multiplexed address and data lines, all running at 33 MHz, providing a total bandwidth of 266 MB/s.
ATA100: The ATA100 logic can achieve read transfer rates up to 100 MB/s and write transfer rates up to 88.9 MB/s and is backwards compatible with ATA66, ATA33 and PIO modes. The cable improvements required for ATA66 are sufficient for ATA100, so no further cable improvements are required when implementing ATA100. Different timings can be programmed for each drive in the system, allowing drives of different types to run at full speed on the same cable.
Small Computer Systems Interface (SCSI): SCSI is the traditional storage channel technology for open system servers. It allows overlapped operations, which means that SCSI Host Bus Adapters (HBAs) can multitask their operations. It supports data intensive applications and a wide variety of devices. SCSI generally spans the midrange product segment.
S-ATA: Serial ATA is another option for high-speed disk connectivity. It offers faster performance than parallel ATA and it is approaching SCSI. It offers thinner cabling, lower power, and lower pin count interfaces vs. ATA or SCSI. S-ATA technology will deliver 150 MB/s of performance to each drive within a disk drive array, and the roadmap specifies 300 MB/s and 600 MB/s throughputs to support generations of storage evolution. The various products and interfaces described above ensure high performance in the proposed NAS appliance design.
NAS Appliance Theory of Operation
A NAS device is essentially a plug-and-play storage appliance, designed to respond to client requests for stored data in real time. NAS devices are well suited to serve networks that have a heterogeneous mix of clients and servers, such as UNIX*, Microsoft Windows*, and Linux*. The NAS appliance can do this by running a suite of file system software compatible with the clients it services. When a client on the LAN requests data from the storage system, the application layer of the client sends a data request over the network to the NAS platform. The local file system of the NAS determines the origin of the request and sends the appropriately formatted data back to the originating client.
A NAS system provides file security, through methods such as Access Control Lists, and it performs all file and storage services through standard network protocols, including TCP/IP for data transfer, Ethernet for media access, and HTTP, CIFS, and NFS for remote file services. In addition, a high-performance NAS appliance may handle tasks such as Web cache and proxy, audio and video streaming, and tape backup.

SOFTWARE CONSIDERATIONS
The building block components of a NAS solution are illustrated in figure below. This section describes the software layers in this solution stack and highlights technical considerations for software implementation.
BIOS and Drivers
In addition to the numerous vendors providing BIOS solutions for Intel processors, equipment manufacturers also develop custom BIOS versions for their particular solution. Original equipment manufacturers may also develop drivers for their own hardware (such as hard drives) or use drivers provided by Intel or other hardware manufacturers.
Operating System
The operating system (OS) manages all the software applications and hardware resources on the system. NAS appliances may use off-the-shelf desktop or server operating systems, such as Windows, Linux, or UNIX, or may utilize an embedded OS, such as Windows CE or Embedded Windows NT*. Another alternative is a real-time operating system (RTOS) such as VxWorks* or QNX*.

NAS Solution Stack
The main considerations for a NAS OS are the size and performance. Desktop operating systems are easier for the customer to implement, but take up more disk space (which means less storage) and also contain unnecessary overhead that usually degrades performance. An RTOS offers a smaller footprint and may even reside in Flash rather than on disk. Development using an RTOS allows for more direct control of the hardware, enabling optimum performance tuning. However, there is a significant investment required in developing with an RTOS. Plus, this may limit the ability to include value-added functionality, such as using the NAS device as a Web server. Embedded operating systems such as Embedded Windows NT are good alternatives because they are modular and provide tools to allow only the necessary modules to be installed. Many Linux packages also have this capability. High Availability (HA) is also becoming a key consideration for OS selection. Linux, for example, has an HA initiative underway.
Application Software and Protocols
The application software layer can be segmented into several functional areas, including services, access permissions, storage, fault tolerance, and networking. Additionally, NAS products may come with client-based tools for setup and access to the NAS device. All functional areas, aside from networking and storage, are value-added capabilities that NAS manufacturers use to differentiate their products.
File Systems
NFS: The Network File System (NFS) is an application that lets a computer user view, update, or store files on a remote computer as though they were on the userâ„¢s local hard drive. Most UNIX and Linux operating systems include NFS client and server software.
SMB: The Server Message Block (SMB) protocol allows a Windows client to access, create, and update files on a remote server. The protocol also allows the same client to access other resources such as printers and mail slots. The SMB protocol can be used over TCP/IP or other network protocols such as IPX and NetBEUI. Microsoft Windows 95 and later versions of the operating system include client and server SMB protocol support. For UNIX and Linux systems, a shareware program called Samba is available. The SMB protocol originated at Microsoft and has gone through a number of developments, eventually evolving into the CIFS standard.
CIFS: Common Internet File System (CIFS) is a standard protocol that enables programs to request files and services on remote computers on the Internet. CIFS is an open variation of SMB. Like SMB, CIFS is built upon the TCP/IP protocol. CIFS is currently the most commonly used protocol for NAS systems because it is readily available on Windows, UNIX, and Linux operating systems, and can also be used in conjunction with Novell* IPX/SPX protocols.
Networking Protocols
Networking protocols control the communication to and from the NAS device. The physical connection of a NAS is Ethernet. Because most NAS devices attempt to homogeneously communicate over the LAN, multiple network protocols are typically supported.
TCP/IP: TCP/IP (Transmission Control Protocol/Internet Protocol) is the basic communication language of the Internet. Many higher-level protocols are built on top of TCP/IP, such as Hypertext Transfer Protocol (HTTP), the File Transfer Protocol (FTP), Telnet, and the Simple Mail Transfer Protocol (SMTP).
IPX/SPX: IPX (Internetwork Packet Exchange) is a networking protocol from Novell that interconnects Novell NetWare* clients and servers. In IPX, packet acknowledgment is managed by another Novell protocol, the Sequenced Packet Exchange (SPX).
AppleTalk*: AppleTalk is a set of proprietary LAN communication protocols originally created for Apple computers. Some NAS systems support the AppleTalk protocol even though more recent Macintosh computers support TCP/IP communications.

PERFORMANCE CONSIDERATIONS
The performance of a NAS device will depend on the storage subsystem, the speed of the network connection, processing speed, and amount of system memory.
RAID-based storage subsystems offer a balance between performance and reliability. While software RAID can provide additional performance and reliability benefits relative to non-RAID implementations, it is not recommended for mission-critical data storage. Hardware-based RAID solutions result in increased performance and higher reliability.
The proposed design also uses Gigabit Ethernet controllers to enhance storage performance. Additional performance gains are possible with an intelligent Gigabit Ethernet controller with TCP/IP offload, which provides the host with additional CPU cycles for processing user requests.

SCALABILITY AND MIGRATION OPTIONS
Host Processor Options
The Pentium III processor not only allows high-performance levels to be achieved, but also brings flexibility and scalability to a NAS appliance.
Implementing dual Pentium III processors can offer a 30 to 50 percent performance gain over a single processor system (dependent on particular hardware and software implementation). Software with multiprocessing and multi-threading capability is required to achieve any performance increase. Utilizing processors of increased core frequencies, ranging from 800 MHz to 1.6 GHz, can further scale the performance of a single system to fit a specific NAS environment.
In addition, the Pentium III processor with 512 KB L2 cache is available in either a 370-pin FCPGA2 (Flip-Chip Pin-Grid Array) or a 479-ball micro-FCBGA (Flip-Chip Ball-Grid Array). The FCPGA2 package uses Socket 370, providing an easy upgrade from previous Intel Architecture processors. In contrast, users of the micro-FCBGA will benefit from the smaller form factor and improved heat dissipation. The advantage of the micro-FCBGA is apparent in dual BGA reference designs, which achieve a complete thermal solution in less than an inch total height constraint.
Storage Subsystem Options
The current protocols used for NAS are all file-level transfer mechanisms. Internet SCSI (iSCSI), however, is a block-based transfer mechanism, giving more direct access to the file systems by bypassing the OS and also removing TCP packet processing. This eliminates significant overhead associated with NFS or CIFS.
Block-based networking will eventually allow NAS devices to efficiently host large databases. For Ethernetbased network storage using iSCSI, network designers can use the Intel® Pro/1000 T IP Storage Adapter. This product uses an Intel XScale processor for offloading TCP/IP and iSCSI operations from the host.
Intel currently offers a family of RAID adapter cards (PCI and modular ROMB) optimized for different server environments. These products showcase Intelâ„¢s I/O processor technology and help system designers achieve quicker time-to-market for server RAID solutions.

SAN and NAS Fundamentals
SANs and NAS are increasingly replacing or supplementing traditional server-attached storage implementations in many data centers. As a result, organizations are realizing a wide range of benefits, including increased flexibility, easier storage deployment, and reduced overall storage costs. Although both SAN and NAS technologies can provide a competitive advantage, each is designed for specific types of environments and applications.

A basic SAN infrastructure using LAN-free data backup
to reduce network traffic

A basic NAS implementation with all data traffic flowing over the production LAN


ANTIVIRUS FOR NAS
In todayâ„¢s networked environments, high availability of data is critical to business success. To enhance availability and accelerate data retrieval, many organizations centralize tremendous volumes of data and make it available via network-attached storage systems to thousands of users across the enterprise. But, when stored data is accessible to distributed users who can download it to their local drives or even email it to others, the risk of spreading viruses rapidly throughout the enterprise becomes a dangerous threat. While it is important to protect the network perimeter, effective protection must also include vulnerable network-attached storage systems. Symantec AntiVirus for network-attached storage devices provides award-winning, unobtrusive virus protection for storage appliances at the center of enterprise networks.
Virus protection for network-attached storage devices
Network-attached storage devices handle large volumes of data, often using proprietary operating systems. As a result, standard fileserver antivirus software may not provide the necessary protection. These devices are designed for high-performance, mission-critical operations and the antivirus software that protects them must be equally fast and scalable. Because of its design as a network available service and its ability to scan high volumes of files per second, Symantec AntiVirus can help prevent network-attached storage devices from becoming a vector for spreading viruses.
Fast, scalable, and reliable
Using Symantecâ„¢s core virus detection and repair technologies, Symantec AntiVirus for network-attached storage devices provides fast, scalable, and reliable network-available antivirus services. Symantecâ„¢s core technologies scale vertically on the same server or horizontally across multiple servers and have been optimized for speed. With its ability to run simultaneously on multiple servers with minimal network impact or latency, it provides fast and scalable protection.
Award-winning antivirus technologies
Symantec AntiVirus for network-attached storage devices leverages Symantec™s award-winning technologies through Symantec AntiVirus Scan Engine to detect viruses, worms, and Trojan horses in all major file types and various compressed file formats. It can also detect malicious mobile code, such as J a v a„¢, ActiveX®, and standalone script-based threats. Symantec Anti-Virus Scan Engine takes advantage of Symantec™s key antivirus engine technologies, including Bloodhound„¢, for the heuristic detection of new or unknown viruses, and NAVEX„¢, which provides protection from new classes of viruses automatically via LiveUpdate„¢”without the need to reinstall software or interrupt virus scanning. LiveUpdate ensures that the latest definitions for detecting and eliminating viruses are delivered regularly and deployed rapidly to protect against newly identified threats.

BENEFITS OF NAS
NAS works well for organizations that need to deliver file data to multiple clients over a network. NAS appliances also function well in environments where data must be transferred over very long distances. Because most NAS requests are for smaller amounts of data, distance and network delays are less critical to data transfer. In addition, NAS appliances are relatively easy to deploy”enabling widespread distribution of NAS hosts, clients, and appliances throughout the enterprise. Properly configured, NAS provides reliable file-level data integrity, because the appliance itself handles file locking. Although deployment is fairly straightforward, organizations must be careful to ensure that appropriate levels of file security are provided during NAS appliance configuration.
A NAS appliance features the following benefits:
Open standards-based interface to data to support requests from clients based on any operating system
Scalable both in system design and by adding NAS appliances to a network
Fast data response times
Easy installation with no down time to the servers or network
Improved reliability
CHAPTER 8
Why are NAS servers faster than the normal file servers
A NAS Server is designed to provide performance file in a heterogeneous networking environment. The NAS operating system is fully optimized for file I/O activity, this makes its faster than a traditional file server which is designed to perform a perform a multitude of functions as well as file serving. Whilst a NAS serverâ„¢s OS code is optimized, it also makes the NAS server OS more reliable and better to file serving, which delivers information faster to the clients.
How reliable are NAS Servers
All the components in a NAS are designed for providing optimized data transfer to the client/ server. Because of the nature of a NAS it has a reduced component count and an optimized OS. These two things make a NAS server more reliable than a traditional file server. Many of the true NAS Servers feature full redundancy and no single point of failure. One major benefit of deploying a NAS server in place of a normal file server is less downtime. Traditional Servers from time to time need upgrading or replacing whether to add more disk drives, processors or memory. This server downtime is not always planned and when it is planned, it is at an inconvenient time or date.
By separating the storage from the server, cost savings can be made by purchasing smaller profile file servers that need less space. If the need arises to upgrade the server processor/memory the important data is held on the NAS and therefore available at all times even though the application sever is being upgraded or replaced. Many of the Network Attached Storage servers offer various levels of RAID configurations. These can be no RAID so the whole useable NAS capacity is available or RAID levels 0,1,5. This ensures that the data is protected in the event of disk failure.
Some of the higher end Network Attached Storage servers also offer high levels of redundancy against component failure. Some of the features found on these models are redundant fans, power supplies, processors, memory and motherboards.
APPLICATIONS AND USES OF NAS
Notebook/Desktop Backup
An increasing amount of valuable information is stored on local hard disks and notebook computers including Outlookâ„¢s PST files, spreadsheets, muti-media presentations, financial information etc. This information costs many times the cost of the hardware but the data is never or rarely backed up. Most NAS devices are now supplied with backup software that automatically backs up the file changes that were made since the last backup to the local NAS device when the user logs in or connects to the network. Should the notebook be stolen or desktop crash due to hard disk failure the data is now available for restore from the network.
Remote Offices
Many small remote offices have numerous client PCâ„¢s and a single server with connection over WAN to HQ. The data on this server should be backed up regularly and removed for safekeeping. Typically what happens is the person in charge of the back ups is on holiday, leaves or off sick and back ups do not get done. Should the server fail no one can now access the server for information. A way to overcome this would be to deploy a NAS device in the local office whereby user access is granted to the data and every night the data is synchronized with the remote office. This way the data is secured off-site and if the server fails users can still access the information locally.

Virtual Disk Library
With ever decreasing backup windows the cost of managing and maintaining a backup of information is becoming problematic. The normal way to increase backup performance and decrease the backup window is to buy faster higher capacity tape drives and automate the backup solution. The problem is cost, unless you have purchased a tape library that can be expanded new tape hardware will need to be bought making your old tape technology obsolete, including all the tapes with the valuable information. A simple cost effective solution could be to deploy a virtual disk library that mimics a real library with slots and cartridge capacities but is based on hard disks. Data can now be packed up at disk-to-disk speeds. When these virtual tapes are full the data can then be transferred to your real tape library and then the tapes stored for safe keeping. Should you need to increase the number of mwedia slots or require additional tape drives all that is needed if to reconfigure the Virtual Tape Library.
7x24 Backup / DR Backup
Most companies perform a backup once a day and typically at night. Should the backup fail for some reason, that night backups are never completed. This is especially critical at weekends when weekly full backups are run. Now herein lies the problem as full backups are run once a week and either incremental or differential are run daily should a server suffer failure, the backup tapes for that server would probably run into many tapes and take considerable time to restore. At best with backups being performed nightly you would loose a days work should server or disk failure occur, if you are an animation house this could run into many lakhs of rupees.
Why not every hour replicate user selected files or entire volumes from one or more source servers to one or more target NAS servers over standard network connections. By doing this the data loss suffered is minimized to the last snap shot backup.
Many companies today have a business continuity or disaster recovery plan. Normally this consists of:
Off-site location
Room full of servers
Backup tapes for restore
Communication links
Networking connections
These organizations then run periodic tests to check that they can recover information and be operating within the minimum time frame.
E-mail Archiving
In light of the recent scandals involving WorldCom, Enron and Tyco regarding the deletion of e-mails, there is currently 63% growth in storage usage attributed to email. Governments now have legislation in place regarding the storing and retrieval of e-mail and attachments for 7 years or more. Many companies have more than 200 employees and backing up either exchange or notes is a major headache for IT departments. The problems are the size of peopleâ„¢s mail boxes grow to utilize all the available disk space available, backups and restores of the whole mail system or individual mail boxes take longer due to the files types and information stored .avi, .jpg ,.mov, .doc, .xls, .mp3 .pst etc.
Why not deploy a NAS server and automatically migrate aged files from the main mail server to the NAS. The user is unaware this has happened as he still sees the files as he would normally with the attachments. By doing this the backups on the mail server will be considerably quicker and in the event of failure the server can be restored much faster.
Reducing Networking Traffic
If you have users within your organization that regularly transfer image files around the network i.e. Movies, graphics, animations, pictures. A solution is to segment the users using a network switch and install a NAS device on their local network segment.
Consolidating servers
A server consists of 4 key components “storage, processor, memory and OS. When you buy a server you would pay for the disk drives, CD/DVD drives, SCSI controllers, RAID controllers, processors, memory, case, tape device and OS license. These servers normally act as file & print servers or run applications. When the server becomes fully populated with disks another server is bought and so the cycle continues. These new servers sit alongside the older server or are complete replacement models. The valuable information stored on these servers then has to be moved/backed up and migrated to the new server all this takes considerable time, looking for service packs, software license numbers, patches, checking the new server will run the same applications as the old etc.
Why not deploy a NAS Server for disk storage or to run applications. These can be easily added and integrated in your existing server framework with the minimum of fuss and no server downtime and be remotely managed via browser. Should you reach the capacity of your NAS Server create a virtual storage pool. For example, you can pool multiple NAS Servers together. Data that is not accessed frequently can be automatically migrated off of critical front-line servers to NAS Server, freeing up overloaded servers for application use. When needed, users have immediate and transparent access to all of their critical stored data with no administrator intervention.
Archival Storage
Traditionally information has been stored on magnetic media, typically in a RAID system. This provides a level of redundancy and fast access to information. On most RAID systems only about 20% of this information is active, the remaining 80% infrequently accessed. When the RAID system is full of information the IT manager has some options to choose:
Install new hard disks “ This creates a problem the server needs to be taken offline whilst the new disks are added formatted and partitioned.
Archive the information “ The problem when Archiving information is what are you actually going to archive Do you send round a memo asking people to let the IT person know what files they frequently use or access The answer is NO! So this is an ineffective way of moving files.
Just delete or copy the files to tape and keep a copy “ This is great if no one wanted to access old information, but in the real world, people will always want to refer to an aged document.
By having RAID systems with data that is infrequently accessed can cause the tape backup system to overrun or span multiple tapes as well as causing unnecessary wear and tear on the drives by backing up the same old files every night.
By implementing a HSM Software solution the user will free up valuable disk space, reduce the backup window, migrating the data to a NAS Server will be able to manage the data storage in a more flexible way.
Software Distribution
How often do businesses need to send software updates to remote offices or stores Some of these updates maybe pricelists, brochure changes, service packs or anti-virus software updates. By having a centralized NAS Server updates can be put on the main office NAS and then these updates can be synchronized to the remote offices for u se. The software works with one-to-many or many-to-one. Another use is estate agents have lots personnel and important data relating to house sales, this information is usually held on the various PCâ„¢s around the office. If you install a small capacity NAS Server, every night this information can be synchronized with the remote office. Should anything happen to the office PCâ„¢s the data is still secured remotely.

APPLICATIONS FOR NAS
There are an estimated 5 million NT 4 servers in the world today with the support ending in 2003, by moving the information from these file servers to NAS Servers will increase productivity and support.
File/Print server
Application specific server
Video Imaging
Graphical image store
Centralized heterogeneous file sharing
File system mirroring
Snap shot critical data
Replacement of traditional backup methods
Medical imaging
CAD/CAM
Portable centralized storage for offsite projects

ADVANTAGES OF NAS
Decreased IT Staff Costs
On the front end, businesses welcome extreme amounts of information and strive to manipulate it for use in real time. On the back end, IT professionals, with their current infrastructures, scramble to accommodate the exponentially increasing data burden. General-purpose servers, especially, require large amounts of skilled personnel time to solve storage and file access challenges.
In contrast, a NAS device requires little IT staff time and effort. Management is accomplished through a graphical user interface (GUI) in a Web browser, which enables NAS access from anywhere on the network. Since a NAS filer is pre-configured to support specific file-serving needs, administration is simplified, and this ease of use results in fewer operator errors. Also, because more capacity can be managed per administrator with NAS than is possible with general-purpose server storage activity, the total cost of ownership is lower.
Scale Fast, Without Downtime
Dot-coms and other rapidly scaling companies endeavor to make sure their IT infrastructures keep pace with their dynamic business realities. Building on the structure of your general server or servers may be required in some business areas. But burdening these servers with escalating storage needs can be ineffective and run counter to your accelerated business practices. As you add capacity for your general-purpose server, you'll face downtime. When you bring the system down to increase its storage, your business applications will be unavailable, which may slow-if not halt-productivity.
On the other hand, expanding storage with NAS is simple and nonintrusive. You can install a new filer within 15 minutes as opposed to hours or days required to install or add traditional storage. More advanced NAS devices can increase storage on-the-fly, eliminating the need for you to add another node on your network. This means your users access what they need when they need it, responding in real time to a marketplace that demands immediate action.
Relief for Your Server
A NAS filer helps by offloading tedious and bandwidth-consuming file serving tasks from your server. This allows your server to use its power to process your data with improved availability and performance. Have you checked your general-purpose server's workload lately If it is handling file-serving activities, chances are it is handling too much. You face increased risk of latency when your general-purpose server must complete high-priority file serving tasks while handling applications, electronic mail, and a myriad of other critical business tasks.
Multi-OS Connectivity and Data-Sharing
Whether your company is busy merging or acquiring, or simply growing, you will no doubt face the demands of a heterogeneous operating environment. A NAS device can answer this challenge with its capability to serve two chief operating system camps: NFS (UNIX) and CIFS (Microsoft Windows). One of the undeniable strengths of NAS is its capacity to support these protocols and allow for cross-platform data sharing. This is an increasingly important attribute as the business usage of data-intensive application files such as digital media (audio, video, and photography) becomes more common.
Leveraging Existing Infrastructure
By adding NAS nodes to your network, you can leverage your network investment and your current network administration skills. NAS can be deployed on your network anywhere it is needed. It also can be integrated with larger management tools, like Microsoft Management Console, Tivoli, and HP Openview, allowing you to maximize your use of these products. And NAS does not require costly network operating system (NOS) licenses.
Often, IT centralization is asked to simplify responsibilities and conserve company efforts, but it accomplishes neither if remote branch and satellite offices must operate without IT support. NAS can help you realize the intent of centralization by allowing you to add storage in a remote office and manage it via the Web-based GUI from anywhere on your network-including your central/home office. This means you can reap higher performance from existing infrastructure at the remote office and keep management "at home."
Transparent Backup
Another benefit of NAS is its transparent backup activities. Filer backup can be completed without affecting the performance of your general-purpose or application servers. Your CPU does not have to calculate what to back up and when. Simply direct your filer to complete backup at a specific time and it will use industry-standard procedures to complete this task.
FUTURE SCOPE
NAS Solutions for Tomorrowâ„¢s Business Issues
IDC predicts that by 2003, more than $6.5 billion will be spent annually on NAS storage solutions. (Source: Taming the Storage Growth Beast with Network-Attached Storage (NAS), ¨ 2000, International Data Corporation.) The analyst group believes the demands of Internet service providers, application service providers, and dot-coms for reliable, cost-effective, and rackable systems will help drive the proliferation of NAS solutions.

CONCLUSION
Focusing processing power solely on file service and storage, NAS filers can serve any business or technology workgroup-from software design to CAD to service providers/dot-coms to engineering-that requires low cost, scalability, and high-performance in a file server. NAS also can work in tandem with your SAN environment, handling network file serving needs while the SAN tackles back-end storage tasks. Unobtrusive and accommodating, filers meld with your existing infrastructure and facilitate data sharing across heterogeneous operating environments. The Internet revolution will push NAS into mainstream. The need for storage connectivity and improved reliability will demand more than other storage media can produce

REFERENCES
¢ Complete Reference of Storage Networks by Robert Spalding
¢ i.t magazine
¢ bitpipe.com
¢ intel.com

ACKNOWLEDGEMENT
I express my sincere gratitude to Dr. Agnisarman Namboodiri, Head of Department of Information Technology and Computer Science , for his guidance and support to shape this paper in a systematic way.
I am also greatly indebted to Mr. Saheer H. and
Ms. S.S. Deepa, Department of IT for their valuable suggestions in the preparation of the paper.
In addition I would like to thank all staff members of IT department and all my friends of S7 IT for their suggestions and constrictive criticism.

CONTENTS
1. INTRODUCTION¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦.. 1
2. NETWORK STORAGE CONCEPTS¦¦¦¦¦¦¦¦¦¦ 3
3. WHAT IS NAS ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦. 6
4. NAS BLOCK DIAGRAM¦¦¦¦¦¦¦¦¦¦¦¦¦¦.. 7
5. FUNCTIONAL DESCRIPTION¦¦¦¦¦¦¦¦¦¦¦¦.. 8
6. SOFTWARE CONSIDERATIONS¦¦¦¦¦¦¦¦¦¦¦ 12
7. PERFORMANCE CONSIDERATONS¦¦¦¦¦¦¦¦¦.. 16
8. SCALABILITY AND MIGRATION OPTIONS¦¦¦¦¦¦. 17
9. NAS AND SAN¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦ 19
10. ANTIVIRUS FOR NAS¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦ 21
11. BENEFITS OF NAS¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦.. 23
12. APPLICATIONS AND USES OF NAS¦¦¦¦¦¦¦¦¦¦ 25
13. APPLICATIONS FOR NAS¦¦¦¦¦¦¦¦¦¦¦¦¦¦. 31
14. ADVANTAGES OF NAS¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦ 32
15. FUTURE SCOPE¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦. 35
16. CONCLUSION ¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦ 36
17. REFERENCES¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦¦.. 37