(06CS833) UNIT-1 STORAGE AREA NETWOKS - VTU notes · (06CS833) UNIT-1 STORAGE AREA NETWOKS . GAURAV.M.NAYAK, LECTURER, DEPT OF CSE, SSE MUKKA Page . 3. More and more companies are

(06CS833) UNIT-1 STORAGE AREA NETWOKS

GAURAV.M.NAYAK, LECTURER, DEPT OF CSE, SSE MUKKA Page 1

UNIT 1

INTRODUCTION

INTRODUCTION: Server Centric IT Architecture and its Limitations; Storage – Centric IT Architecture and its advantages. Case study: Replacing a server with Storage Networks; The Data Storage and Data Access problem; The Battle for size and access.

SERVER-CENTRIC IT ARCHITECTURE AND ITS LIMITATIONS

With a neat diagram, explain the server centric IT architecture and bring out its limitations.

(JUNE 2012, JUNE/JULY 2011) (10marks) In conventional IT architectures, storage devices are normally only connected to a single server. To increase fault-

tolerance, storage devices are sometimes connected to two servers, with only one server actually able to use the

storage device at any one time.

In both cases, the storage device exists only in relation to the server to which it is connected. Other servers cannot

directly access the data; they always have to go through the server that is connected to the storage device. This

conventional IT architecture is therefore called server-centric IT architecture. In this approach, servers and storage

devices are generally connected together by SCSI cables.

In conventional server-centric IT architecture storage devices exist only in relation to the one or two servers to

which they are connected. The failure of both of these computers would make it impossible to access this data. Most

companies find this unacceptable. At least some of the company data (for example, patient files, and websites) must be

available around the clock.

Figure 1.1 In a server-centric IT architecture storage devices

exist only in relation to servers

Figure 1.2 The storage capacity on server 2 is full. It cannot make use of storage space free on server 1 and server 3

is still storage space free on server 1 and server 3

www.bookspar.com | VTU NOTES | QUESTION PAPERS | NEWS | VTU RESULTS | FORUM | BOOKSPAR ANDROID APP




Although the storage density of hard disks and tapes is increasing all the time due to ongoing technical

development, the need for installed storage is increasing even faster. It is necessary to connect ever more storage

devices to a computer. But each computer can accommodate only a limited number of I/O cards (for example, SCSI

cards). Furthermore, the length of SCSI cables is limited to a maximum of 25 m. This means that the storage capacity

that can be connected to a computer using conventional technologies is limited.

In server-centric IT environments the storage device is statically assigned to the computer to which it is connected.

In general, a computer cannot access storage devices that are connected to a different computer. This means that if a

computer requires more storage space than is connected to it, it cannot still use the free space present in another

computer.

Storage devices are often scattered throughout an entire building or branch. Computers may be consciously set up

where the user accesses the data in order to reduce LAN data traffic. The result is that the storage devices are

distributed throughout many rooms, which are neither protected against unauthorized access nor sufficiently air-

conditioned.

Paragraphs 3,4,5,6 contain the limitations.

STORAGE-CENTRIC IT ARCHITECTURE AND ITS ADVANTAGES

Explain with a neat diagram, the working and advantages of storage centric IT architecture.

(JUNE 2012) (10marks)

Storage networks can solve the problems of server-centric IT architecture. Storage networks open up new

possibilities for data management.

The idea behind storage networks is that the SCSI cable is replaced by a network that is installed in addition to the

existing LAN and is primarily used for data exchange between computers and storage devices.

In contrast to server-centric IT architecture, in storage networks storage devices exist completely independently of

any computer. Several servers can access the same storage device directly over the storage network without another

server having to be involved.

Storage devices are thus placed at the centre of the IT architecture. IT architectures with storage networks are

therefore known as storage-centric IT architectures.

When a storage network is introduced, the storage devices are usually also consolidated. This involves replacing the

many small hard disks attached to the computers with a large disk subsystem.

Disk subsystems currently have a maximum storage capacity of several ten terabytes. The storage network permits

all computers to access the disk subsystem and share it.

Free storage capacity can thus be flexibly assigned to the computer that needs it at the time. In the same manner,

many small tape libraries can be replaced by one big one.





More and more companies are converting their IT systems to a storage-centric IT architecture. It has now become a

permanent component of large data centers and the IT systems of large companies. More and more medium-sized

companies and public institutions are now considering storage networks.

Depending upon the source, it is predicted that by the end of 2004 two-thirds of external storage capacity will be

connected by means of storage networks.

CASE STUDY: REPLACING A SERVER WITH STORAGE NETWORKS

Explain with a neat diagram, the replacing of a server with Storage Networks (8-10marks) In a production environment an application server is no longer powerful enough. The ageing computer must be

replaced by a higher-performance device. The procedure is complicated in a conventional, server-centric IT

architecture; it can be carried out very elegantly in a storage network.

Before the exchange, the old computer is connected to a storage device via the storage network, which it uses

partially (Figure 1.4 shows stages 1, 2 and 3).

First, the necessary application software is installed on the new computer. The new computer is then set up at

the location at which it will ultimately stand. With storage networks it is possible to set up the computer and

storage device several kilometers apart.

Next, the production data for generating test data within the disk subsystem is copied. Modern storage systems

can (practically) copy even terabyte-sized data files within seconds. This function is called instant copy.

Then the copied data is assigned to the new computer and the new computer is tested intensively.

After successful testing, both computers are shut down and the production data assigned to the new server.

The assignment of the production data to the new server also takes just a few seconds.

Figure 1.3 In storage-centric IT architecture the SCSI cables are replaced by a network. Storage devices now exist independently of a server

is still storage space free on server 1 and server 3





Finally, the new server is restarted with the production data.

THE DATA STORAGE AND DATA ACCESS PROBLEM

THE CHALLENGE OF DESIGNING APPLICATIONS

Storing and accessing data depends on the business application.

Recognizing the function of application design in today’s component driven world is a challenging task, these

functions are necessary to facilitate user data within applications.

The basic idea is the storage strategy used.

Most designers just note the type of database or databases required, be it a relational or non-relational.

The choice of database depends on economic, type of application or existing infrastructure etc.

The choice of database leads to the overall interaction of the application with the storage device.

Applications are dependent upon memory management (RAM, Cache), file systems, relational and non

relational database systems.

Figure 1.4 Steps 1, 2, and 3

is still storage space free on server 1 and

server 3

Figure 1.5 Old server and new server share the storage system. The new server is intensively tested using the copied production data (4)

Figure 1.6 Finally, the old server is powered down (5) and the new server is started up with the production data (6)





Most business applications don’t consider the complexity of storage performance factors in their design

activities.

Business applications will show non linear performance.

NON LINEAR PERFORMANCE IN APPLICATIONS

The reasons for non linear performance is due to :

i) The availability of sufficient online storage capacity for application data coupled with sufficient temporary

storage resources. (RAM, Cache etc).

Online storage is the mechanism that allows users to interact with an application, and information is available

in real time.

The amount of online storage required depends on user data, data requirement of the application etc.

When users submit data, there must be locations where the application can temporarily store data before

transaction completes the execution, so RAM, cache are used for temporary storage. (Figure 1.9)

ii) The number of users who will interact with the application and thus access the online storage for application

data retrieval and storage of new data.

The number of user transactions accessing the storage resources corresponds linearly to the amount of time

each transaction takes to complete.

Even in diverse applications, transactions depend on storage infrastructure and also on the server computing

capacity and network capability.

Figure 1.7 Database choices for applications

Figure 1.8 Components that effect application performance





Therefore configurations can be developed so a fixed number of users will be serviced within an acceptable

response-time window.

Figure 1.10 shows the no of user transactions accessing storage resource will correspond linearly to the amount

of time each transaction takes to complete.

THE CLIENT /SERVER STORAGE MODEL

Figure 1.11 shows the users logged into their client computers and accessing the N/W server. The N/w server is

used to store information and process the same.

The C/S storage model provides data storage capabilities for the server component as well as storage for the

network clients.

When online storage is used with high performance servers, (increased RAM and cache) storage devices are

used by clients for faster access of data.

Servers reach its maximum capacity as client demand increases.

Sharing information on server increased the need for capacity, requiring networks to use multiple servers.

This is due to the need for online storage to handle the growing amount of data. So no of servers increased.

This led to server specialization. The N/W servers had handle clients, keep their profiles & manage N/W

resources which led to the demand for database server.

The relational database model became pervasive; the amount of databases within the N/W grew exponentially.

Figure 1.9 online storage for applications

Figure 1.10 The optimum configuration of user transactions verses

storage resources





The database server model needed servers to be more robust & powerful. This involved large amounts of RAM,

caches & storage resources.

As data grows storage solutions with client/server storage model continued to be problematic.

Growth rates began to show a varied and asymmetrical growth trend, some servers were deployed with more

storage than required, wasting space or in other cases some servers may not perform due to less space.

Figure 1.13 shows the complexities in data warehouse.

Data warehouse is use as a target market application that ensures customers with good credit are selected &

matched with offerings for financial investments. These matches are stored & targeted for mailings in which

responses are tracked.

The data traverses from online storage “A” on server A, where the customer activity and tracking database

resides, to populate the data warehouse online storage “B” on server DW. The selection of good customers

from server A populates the database on server DW’s online storage “B” where it is matched with financial

investment product offerings also stored on Server A. the aggregate data on C is developed from combining

good customers on server B to from a mailing & tracking list stored on server DW’s online storage “C”.

As data grow, so does user access. The biggest challenge is the internet which is based on the Client/server

storage model.

Web server s began to grow due to the ease of developing web pages, the amount of users able to connect

web server became limited only by addressing and linking facilities.

Figure 1.14 shows how web servers specialize in user access, user profiles & accounts, web pages & mail

Figure 1.11 The client / server storage model

Figure 1.12 Database server configurations





Internet service providers (ISP) support web based applications & provide access to the internet for the users.

The data traverses from online storage on web server A, where user authentication & access takes place, then

moves to online storage on web user servers where profiles & home pages are stored.

If the request is to check email, the web user transfers the request to the web mail server where request is

placed in an index & transferred to the location of the user’s mail.

If the requested web page is not present in the web server A & B it will locate the web page in the outside

servers & transmit the web page to the customer’s PC.

REACHING THE CLIENT/ SERVER STORAGE LIMITATIONS

Data centric applications, data warehouses & ISPs demonstrate the Client/ Server storage model.

The disk drives are becoming smaller & are holding large amount of data. Caches have advanced. So there

cannot be I/O limitations of Client/ Server architecture.

The amount of servers we have has far exceeded our capability to manage the attached storage.

More & more users are coming online through Internet based capabilities.

Increased functionality & access to a diversity of data has created an informational workplace.

Our own individual demands to store more & more data are pushing the limits of computer networks.

It will be an increasing challenge to accommodate a global online community a global online community

with client/ server storage configurations.

Figure 1.13 Data moving through warehouse application

Figure 1.14 Web Server Storage





THE BOOT DISK OF INNOVATION

The data flow changes have historically been the “Boot Disk” of innovation. This has prompted the industries to

address the data storage/ data access problems & also to respond to client/ server storage model.

Attempts like combining the elements from the storage world with innovation from the networking

technologies were done by the industries to address the problems.

Thus storage networking was formed, which combines the aspect of previous ideas & technologies in a totally

different manner.

It changes by moving the storage from a “direct” connection to the server to a “Network” connection.

It places the storage directly on the network. It provides a basis for dealing with non linear performance factors

of applications.

It lays foundations for larger data access tasks, share data across servers & management of larger online

storage capacities.

THE BATTLE FOR SIZE AND ACCESS In traditional systems (C/S) storage devices are directly connected to the server (Figure1.15).

All communications with the data stored on the storage devices to be handled by the server, which resulted in

a tremendous overhead on the server.

Storage networks changed this feature by allowing storage devices connected directly to a network.

This created two important changes to traditional storage configurations.

i) It provides direct access paths between storage devices, servers and clients. User transactions can go more

directly to the data. Without unnecessary access to the server.

ii) Storage networking grants business applications greater access to data with increased efficiency.

Storage N/Ws makes it easier to share data, allowing servers to connect to larger amount of data.

Figure 1.15 Directly connected storage

in C/S model

Figure 1.16 NAS showing enhancements to data access

Figure 1.17 SAN showing enhancements to data size





Storage Networking has 2 models. Network Attached Storage (NAS) & Storage Area Networks (SAN).

NAS allows storage to be placed onto an existing client/ server network based on Ethernet standards using

TCP/ IP protocols (Figure 1.16).

SAN creates a unique network for storage which is based on a protocol called Fibre Channel (Figure 1.17).

METRO DATA AREAS

Our data is stored in large server farms that produce circumstances similar to those in large metropolitan area,

policing, and monitoring performance, security, handling overcrowding & occasional accident.

Powerful servers connected to larger storage systems. The complex network of highways (internet) allows users

to access data regardless of locations or specific storage systems.

Metro data areas will be located in corporate data centers, Internet service provider infrastructures, govt &

public institutions.

Metro data area will have 100% annual growth & will be driven into the next generation of storage technology

which will handle the tremendous amount of data moving in & out of these areas.

WHY STORAGE NETWORKING MAKES SENSE

Why storage networking is needed? (4marks)

Many IT organizations comment on their applications “we have bigger data, more sources and need a single

distribution strategy”.

Bigger data: The data stored and transferred between storage and server is larger in size, the amount of data

transferred between server and client is also larger.

More sources: The application must work on several sources of data to satisfy the client transaction. I.e. server

has to connect with several storage sources.

Single distribution strategy: the results of the application need to be placed in a central location for access.

This means internet accessibility.

THE PROBLEM: SIZE, ACCESS

With the solutions explain the problems faced by IT organizations in terms of Size & Access?

(6marks)

The Problem: Size Many IT organizations say “we must have wider bandwidth for data transfers from storage the

problem is size. The databases we work are exceeding the limitations of the server’s storage connectivity”.





Wider bandwidth is needed: the connection between server and storage unit requires a faster data transfer

rate. In Client server storage model the data transfer rate is limited to about 10MBPS.

The problem is size: The database and supporting online storage has limitations, resulting in lagging requests

for data & subsequent unresponsive applications.

Solution: Storage networking enables faster data transfers as well as the capability for servers to access larger

data stores.

The Problem: Access

Many IT organizations say “the real problem is access; we don’t have sufficient resources to access the application

server. This will get worse if we go to a single distribution strategy.”

The Problem is Access: There are too many users for the supported configuration. A large number of user

transactions cannot be delivered to the server by the network and cannot be responded in a timely manner.

The single distribution strategy: A single distribution strategy can create an information bottleneck.

Solution: With storage networking, user transactions can access data more directly, bypassing I/O operations

and overhead involved with server.

BUSINESS APPLICATIONS DEFINED FOR STORAGE

Business applications or enterprise business applications will be most affected by and find value in storage

networking. We must first define an enterprise business application, as well as differentiate it from maintenance

applications & support programs.

Enterprise business applications are complex, scalable, distributed & component based.

They are data centric & user friendly. Meets security, administration & maintenance.

There are 3 specific attributes:

Large: Along lived, multiuser, multi developer, multi machine & multi component application that can

manipulate massive data & utilize extensive parallel processing.

Business oriented: To meet specific business requirements, the application encodes business policies, process,

rules& entities is developed in a business organization.

Mission critical: An enterprise business application must be robust enough to sustain continuous operations,

be flexible for scalability & deployment that allows effective maintenance & administration.

MAINTENANCE & SUPPORT APPLICATIONS

Supporting large, highly available business applications & their infrastructures are numerous

maintenance & support applications. They are implemented within support infrastructure areas.

It is important to differentiate between these 2 distinct types of applications.

This difference is important due to IT organizational boundaries that focus on IT specialties between

programming & design personnel.





The support applications have the following distinct attributes:

Their results are focused upon supporting & maintain server platforms & components that create a continuous

operational infrastructure.

They have enhanced IT abilities to maintain levels of reliability, availability & serviceability for the data center.

The usage of support applications provides necessary information to maintain a scalable & manageable data

center.

The tools & products within these areas defined as storage management applications can be defined by:

Archive/ Backup/ Recovery: Provides IT with tools to initiate data protection policies that copy data & provides

recovery mechanisms.

Storage Resource Management: Enhances the usage of resources that make up the storage infrastructure. It

includes monitoring the stored data.

Storage Data Management: complement the storage infrastructure with enhancements to file/systems, fault

tolerance & data optimization, compression.

Storage Security: it is related to user authentication & resource access technologies.

BUILDING THE BUSINESS APPLICATION

The application designers concentrate on business requirements & produce a requirement document which

determines what will produce to end users at the completion of the development process.

The document which is signed off, will used for external design document which consists of an external view of

end user functions, access points & outputs.

This is followed by internal design activities where the logic & external S/W development components to be

used are identified.

During the internal design process the application designers & programmers work with database administrators

to provide a logical design for application data.

The design is followed by an iterative process of building the application by the application programmers.

Unit testing is performed & then integrated with other components to form a major function of the application

system.

All the components are integrated & tested in terms of system testing, which is followed by user testing where

end users test the system for accuracy& functionality.

Once the system is completely tested the system moves into production mode.

Under production mode certain entities like migrating users from old systems into new systems is seen.

Now it’s a matter how application works with an unknown server& storage infrastructure.





A third process in the application development cycle is post- implementation analysis & understanding of real

storage & data access requirements of the application system.

The third process requires 2 major pieces of information. First is the availability of storage solutions to offer to

the application designers. Secondly a detailed model understanding of input & output processes.

BENEFITS OF STORAGE NETWORKS ON BUSINESS APPLICATIONS

Briefly discuss the befits of storage networks on business applications (10marks)

(JUNE/JULY 2011)

Scalability of access to business application data:

Figure 1.19 demonstrates the shift from centralized data access to networked data access for SAN & NAS

configurations. Here more servers can connect and utilize storage devices concurrently, thereby reduces the

complexities and overhead involved in maintaining multiple copies of data from each server. Allows centralized access

to the data associated to the application & eliminates single point of failure problem of applications.

Consolidation of business application data:

Since maintaining multiple, synchronized copies of data is no longer necessary, storage devices previously

connected directly to servers are used by more multiple servers. Storage devices can be used more efficiently by

serving multiple servers with multiple sets of data. This eliminates copying and synchronization process and increases

business application availability by decreasing down times.

Figure 1.18 The application development life cycle





Faster access to Data through improved bandwidth and centralized configurations:

The increased bandwidth associated with moving to storage network configurations has clear advantages in the

amount of data transferred. Here data movement is faster due to the Usage of fiber channel protocol (SAN). NAS

environment also offer increased speed when separate sub network is used. Both the technologies allow for

configurations that can sustain in an increased no of business application transactions.

Increased business application availability through efficiencies in storage management:

Figure 1.20 demonstrates the capabilities of devices with in a SAN configuration to communicate with each other

thereby allowing many of the servers based, data centric maintenance/support applications are optimized. Support

applications are offloaded from the server, i.e. data can be copied from storage network device to another storage

network device (Disk to disk, disk to tape etc). This improves the availability of business applications .In NAS device to

device communication is not possible unlike SAN.

Figure 1.19 Moving to Networked data access with a SAN

Figure 1.20 Device to device communication within a SAN







Documents

(06CS833) UNIT-1 STORAGE AREA NETWOKS - VTU notes · (06CS833) UNIT-1 STORAGE AREA NETWOKS . GAURAV.M.NAYAK, LECTURER, DEPT OF CSE, SSE MUKKA Page . 3. More and more companies are