STORAGE AREA NETWORK   (SAN)
After completing this unit, you will be able to:
·         Understand Storage Area Network.
·         Understand Network Attached Storage.
·         Understand Voice Over Internet Protocol.
·         Understand deficiencies of the traditional methodology of Data Storage.
·         Understand the optimum use of the Protocols especially TCP/IP.
A.1 Introduction
A.2 Storage Area Network
A.3 Benefits of Storage Area Network
A.4 Network Attached Storage
A.5 Network Attached Storage Vs Traditional File Servers
A.6 Network Attached Storage Vs Storage Area Network
A.7 Voice Over Internet protocol
A.8 Summary
The field of networking is always noticing the remarkable progress in each and every area namely layout, design, system, security, storage etc. Such a progress is noticed in the technology as far as storage is concerned examples Storage Area Network and Network Attached Storage. The technology savvy people are also ensuing optimum and efficient use of the protocols developed to handle communication in a network based environment, such a development is VoIP voice over internet protocol.
A Storage Area Network (SAN), in its purest sense, is a separate computer network, typically based on a fiber channel, switches and hubs that connect storage devices to a heterogeneous set of servers for sharing resources. A SAN can also enable direct storage-to-storage interconnectivity, and lends itself exploiting new breeds of clustering technology and to get the best out of Network devices.
The technologies that constitute a Storage Area Network are as follows. The critical enabler is fiber technology. This is the ability to send data across fiber optic channels at very high speeds and bandwidths to sites as far away as 10 kilometers. Fiber enabled servers, disk arrays and other intelligent storage and other devices are then connected by fiber through sophisticated switches and hubs. These are configured in highly scalable manner to provide access from hundreds of servers in many locations to hundreds of terabytes of shared storage resources attached directly to the Storage Area Network.
What these technologies do is enable the removal of storage devices from their servers and make the storage generally available across the network on a ‘many to many’ basis.
In its simplest form Storage Area Network simply provides server to storage access across fiber. In a more sophisticated form Storage Area Network enables a disk or tape array to be accessed by two or more servers at high speed across the fiber channel. The benefits of this include Improved Performance, Greater Connectivity and the elimination of redundant data. A Storage Area Network also expedites the use of advanced clustering solutions thereby enabling new levels of availability and business continuity. A Storage Area Network also enables us to relocate backup, restore, file migration and replication of data from the servers and local/wide-area networks and have direct data movement from disks/tapes to other disks/tapes across the Storage Area Network fiber.

·         Backups done quietly behind the scenes without disturbing the routines.
·         Server power is freed up for the business applications.
·         Network capacity is released for the users for optimum utilization.
·         Remote disaster recovery utilities, etc.
All this is possible without having to change existing applications, database management systems or the way the user connects to their applications via their current local area network the change only here is that the storage is simply moved away from the servers onto its own network and the applications will be delivering ‘local’ speed of access to data on the Storage Area Network where the data may infact be many kilometers away.
In other words, a Storage Area Network represents the removal of storage from their servers and makes the storage generally available across the network.
An alternative and interesting way to visualize a Storage Area Network is shown in Fig. A.1The Storage Area Network is shown within the center. This is where the corporate data resides - a pool of shared on-line, off-line and intelligent storage devices made available via the fiber channel(s).
                                                       Fig A.1
Users connect via a Local Area Network (LAN) and/or Wide Area Network (WAN) through the application servers into the data. In this way we can see that the application server is simply acting as an access path into the data. Rather than connecting to, for example, the email server we are accessing our email data through the server. Further, if we have a suitable architecture, then should the application server fail, compatible spare server capacity can take over the user processing needs easily. This is a crucial point to note - this new storage topology facilitates a new architecture for enhancing availability, and leads us to the interesting concept those application servers in a Storage Area Network aware cluster can be considered as ‘Application Server Peripherals’ around the users data. It also shows that the typical ‘failover’ high availability solution of today that requires 100% redundant hardware can be replaced by one where, say, a 32-machine cluster can enable each server to provide ‘application takeover’ facilities for its peers. This provides equal or better availability with far less hardware.
This new architecture provides a number of significant benefits:
1.       Increased Flexibility
Isolated data sources can be interconnected and made generally available to multiple servers. The limit for how far apart these sources can be is defined by the enabling infrastructure of the fiber channel itself. This facilitates the re-use of storage in a more efficient manner than ever before. Indeed, through the Storage Area Network architecture, we can consider allocating storage from one application to another even though the applications are running in different physical locations. The result is a far better return on investment from our existing infrastructure.
2.       Improved Scalability
Servers and their associated storage are no longer tightly linked together. New storage devices can be dynamically added to the central pool of storage, without having to add a new server. In a similar way, additional servers can be dynamically added, based on additional requirement of processing power for our applications.
3.       Improved Performance
High performance access to global data is achieved because of the inherent performance characteristics of the enabling fiber channel technology. In addition, the Storage Area Network architecture makes it possible to relocate various activities such as backup, restore, file migration and replication of data. Instead of passing data across the local/ wide-area networks via servers, we have the opportunity to move the data directly from disk/tapes to other disks/tapes across the Storage Area Network fiber. In this way, server power is freed up for the business applications and network capacity is released for the users.
4.       Improved Availability
The Storage Area Network dramatically improves availability of business processing. For example, any server can take over from a failed applications server - as they, share access to the same storage and users. We are no longer constrained by bottlenecks in terms of how we get to our data - we can now reach our corporate data through any application server because of improved clustering solutions. It addition, data can be automatically replicated to where it is needed in business terms .Technology is now becoming available that will enable such replication to occur at either the disk/volume level or at the database/file-system level. For the really critical applications, a change of data value can be updated on all replicas simultaneously. A fundamental utility within the Storage Area Network is a set of replication facilities to meet these needs. These replication facilities must be completely accurate, reliable and exhibit very high performance and thereby give the company confidence to remove all the ‘private’ copies that probably exist to date. Hence the Storage Area Network model provides inherent availability of data by the use of automatic data redundancy, automatic backups and the maintenance of nearby disaster recovery copies. Clustered servers with shared access to the data that can dynamically switch users (and applications) between peers will dramatically improve user and business application availability.
5.       Improved Manageability
In many senses Storage Area Networks lend themselves to improved management by their inherently better reliability and ‘centralization’. Whereas previously the storage was ‘hidden’ behind specific servers, it is now generally available. This is inherently safer and simpler to manage.
Automated monitoring and management tools can identify faults, isolate the cause and automatically fix them - without human intervention and with imperceptible effect on the service. Other than data redundancy for resilience purposes, the Storage Area Network enables duplicate data to be removed, saving on total disk capacity needed. Utilities like backup and replication can then be carried out within the storage pool.
6.       Improved Reliability
Inherent within a Storage Area Network structure is RAID disk and tape technology for both improved reliability and performance. Fiber channels and sophisticated switched fabric technology ensure no single point-of-failure on the network component, Further, over time, STORAGE AREA NETWORK technology will provide the ability to replace or repair any component during normal operation, reconfigure the system, add new components and otherwise enable the vast majority of changes to be made on the fly.
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. Home computer users, with the advent of MP3 music files and JPEG images scanned from photographs, likewise require greater and more convenient storage than earlier.
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.
To overcome these deficiencies, several new methods of utilizing computer networks for data storage have emerged in recent years. One popular approach, Network Attached Storage (Network Attached Storage), allows homes and businesses to store and retrieve large amounts of data with ease than ever before.
What Is Network Attached Storage?
NAS differs than 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, Network Attached Storage designs begin with the barebones components necessary to support file transfers and add features “from the bottom up”.
Like traditional file servers, Network Attached Storage follows a client/server design. A single hardware device, often called the Network Attached Storage box or Network Attached Storage head, acts as the interface between the Network Attached Storage and network clients. These Network Attached Storage 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 Network Attached Storage systems to increase total capacity. Clients always connect to the Network Attached Storage head, however, rather than to the individual storage devices.
Clients generally access a Network Attached Storage over an Ethernet connection. The Network Attached Storage appears on the network as a single “node” that is the IP address of the head device.
A Network Attached Storage 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 Network Attached Storage are parallel to those of traditional file servers.
Network Attached Storage 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.
NAS Protocols
Communication with a Network Attached Storage 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 Network Attached Storage are Sun Network File System (NFS) and Common Internet File System (CIFS). Both NFS and CIFS operate in client/server fashion. Both predate the modem Network Attached Storage by many years; original work on these protocols took place in the 1980s.
NFS was developed originally for sharing files between UNIX systems across a LAN. Support for NFS soon expanded to include non-UNIX systems; however, most NFS clients today are computers running some flavor of the UNIX operating system.
The CIFS was formerly known as Server Message Block (SMB). SMB was developed by IBM and Microsoft to support file sharing in DOS. As the protocol became widely used in Windows, the name changed to CIFS. This same protocol appears today in UNIX systems as part of the Samba package.
Many NAS systems also support Hypertext Transfer Protocol (HTIP). Clients can often download files in their Web browser from a Network Attached Storage that supports HTTP. Network Attached Storage systems also commonly employ HTTP as an access protocol for Web-based administrative user interfaces.
Proponents of NETWORK ATTACHED STORAGE claim that NETWORK ATTACHED STORAGE technology provides these advantages over traditional file servers:
1.       Lower cost.
2.       Better security.
3.       Higher availability (less downtime).
4.       Easier to use and administer the network access.
Network Attached Storage 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 Network Attached Storage device becomes less prone to system “crashes” and security attacks. When a problem does occur, a Network Attached Storage system can be diagnosed and rebooted much faster due to its lower level of complexity. .
Network Attached Storage 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, Network Attached Storage systems strive for greater operating system independence of clients.
Opponents of Network Attached Storage emphasize that traditional file servers have a proven record of success compared to this new breed of “upstart” Network Attached Storage systems. High-end file systems also contain more processing power than a Network Attached Storage device, giving servers a performance edge (in terms of transactions or I/O per second rates) over Network Attached Storage.
At a high level, Storage Area Networks (SAN) serve the same purpose as a Network Attached Storage (NAS). A Storage Area Network supplies data storage capability to other network devices. Traditional Storage Area Networks differed from traditional Network Attached Storage in several ways. Specifically, Storage Area Networks often utilized Fiber Channel rather than Ethernet, and a Storage Area Network often incorporated multiple network devices or ‘endpoints’ on a self-contained or ‘private’ LAN, whereas Network Attached Storage relied on individual devices connected directly to the existing public LAN. The traditional Network Attached Storage system is simpler network storage solution, effectively a subset of a full Storage Area Network implementation.
The distinction between Network Attached Storage and Storage Area Network has grown fuzzy in recent times, as technology companies continue to invent and market new network storage products. Today's Storage Area Networks sometimes use Ethernet, Network Attached Storage systems sometimes use Fiber Channel, and Network Attached Storage systems sometimes incorporate private networks with multiple endpoints. The primary differentiator between Network Attached Storage and Storage Area Network products now boils down to the choice of network protocol. Storage Area Network systems transfer data over the network in the form of disk blocks (fixed-sized file chunks, using low-level storage protocols like SCSI) whereas Network Attached Storage systems operate at a higher level with the file itself.
VoIP, or Voice over Internet Protocol, is a method for taking analog audio signals, like the kind you hear when you talk on the phone, and converting them into digital data that can be transmitted over the Internet,
Voice over Internet Protocol can turn a standard Internet connection into a way to make free phone calls. The practical upshot of this is that by using some of the free Voice over Internet Protocol software that is available to make Internet phone calls, you are bypassing the phone company (and its charges) entirely.
Voice over Internet Protocol is basically a clever ‘reinvention of the wheel.’ The principles behind Voice over Internet Protocol is its applications and the potential of this emerging technology, which will more than likely one day replace the traditional phone system entirely.
Voice over Internet Protocol Calling
The interesting thing about Voice over Internet Protocol is that there is not just one way to manage a call. There are three different ways of Voice over Internet Protocol service:
1.       ATA
The simplest and most common way is through the use of a device called an ATA (analog telephone adaptor). The ATA allows you to connect a standard phone to your computer or your Internet connection for use with Voice over Internet Protocol. The ATA is an analog-to-digital converter. It takes the analog signal from your traditional phone and converts it into digital data for transmission over the Internet. You simply crack the ATA out of the box, plug the cable from your phone that would normally go in the wall socket into the ATA, and Voice over Internet Protocol calling can be initiated.

IP Phones
These specialized phones look just like normal phones with a handset, cradle and buttons. But instead of having the standard RJ-11 phone connectors, IP phones have an RJ-45 Ethernet connector. IP phones connect directly to your router and have all the hardware and software necessary right onboard to handle the IP call.
This is certainly the easiest way to use Voice over Internet Protocol. You don't even have to pay for long-distance calls. There are several companies offering free or very low-cost software that you can use for this type of Voice over Internet Protocol. All you need is the software, a microphone, speakers, a sound card and an Internet connection; preferably a fast one like you would get through a cable or DSL modem. There is usually no charge for computer-to-computer calls, no matter the distance.
Voice over Internet Protocol features:

You can make a call from anywhere you have broadband connectivity. Since the IP phones or ATAs broadcast over the Internet, they can be administered by the provider anywhere there is a connection. So business travelers can take their phones or ATAs with them on trips and always have access to their home phone. Another alternative is the soft phone.
A soft phone is client software that loads the VoIP service onto your desktop or laptop. The Vonage soft phone has an interface on your screen that looks like a traditional telephone. As long as you have a headset/microphone, you can place calls from your laptop anywhere in the broadband-connected world.
Voice over Internet Protocol phones are more economical than mobile phones or any other telecommunication devices it VoIP includes facilities like:
·         Caller ID
·         Call waiting.
·         Call transfer
·         Repeat dial
·         Return call
·         Three-way calling
There are also advanced call-filtering options available from some carriers. These features use caller ID information to allow you make a choice about how calls from a particular number are handled and you can:
·         Forward the call to a particular number
·         Send the call directly to voicemail
·         Give the caller a busy signal
·         Play a “not-in-service” message
·         Send the caller to a funny rejection hotline
Limitations of Voice over Internet Protocol

One of the major flaws in VolP is reliability.
First of all, Voice over Internet protocol is dependent on wall power. Your current phone runs on phantom power that is provided over the line from the central office. Even if your power goes out, your phone (unless it is a cordless) still works. With Voice over internet Protocol, no power means no phone. A stable power source must be created for Voice over Internet Protocol.
Another consideration is that many other systems in your home may be integrated into the phone line. Digital video recorders, digital subscription TV services and home security system s all use a standard phone line to avail the benefits. There is currently no way to integrate these products with Voice over Internet Protocol.
Because Voice over Internet Protocol uses an Internet connection, it is susceptible to all the hiccups normally associated with home broadband services. All of these factors will affect call quality:
·         Latency
·         Jitter
·         Packet loss
Phone conversations can become distorted, garbled or lost because of transmission errors. Some kind of stability in Internet data transfer needs to be guaranteed before Voice over Internet Protocol could truly replace traditional phones.
·         Voice over Internet Protocol is susceptible to worms, viruses and hacking.
·         Another issue associated with Voice over Internet Protocol is having a phone system dependant on individual PCs of varying specifications and power. A call can be affected by processor drain. Let's say you are chatting away on your softphone, and you decide to open a program that saps your processor. Quality loss will become immediately evident. In a worst case scenario, your system could crash in the middle of an important call. In Voice over Internet Protocol, all phone calls are subject to the limitations of normal computer issues.

In this unit, we have focused on the area of advancements in the field of networking with respect to areas such as layout, design, system, security, storage, etc. Major changes have been noticed in the technology as far as storage is concerned. Organisations and technology savvy people are ensuing the optimum and efficient use of the protocols developed to handle communication in a network based environment. One such major development is VoIP (voice over internet protocol).
A Storage Area Network (SAN) in its purest sense, is a separate computer network, typically based on a fibre channel, switches and hubs that connect storage devices to a heterogeneous set of servers for sharing resources.
NAS differs from 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 adds features "from the bottom up."
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. Clients always connect to the NAS head, however, rather than to the individual storage devices.
VoIP, or Voice over Internet Protocol, is a method for taking analog audio signals, like the kind you hear when you talk on the phone, and converting them into digital data that can be transmitted over the Internet.