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Note for Computer Network - CN By New Swaroop

  • Computer Network - CN
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  • University of mysore - Gangotri
  • Computer Science Engineering
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STORAGE AREA NETWORKS (10CS765) Unit No.: 01 - Introduction to Information Storage and Management, Storage System Environment Introduction Information is increasingly important in our daily lives. We have become information dependents of the twentyfirst century, living in an on-command, on-demand world that means we need information when and where it is required. We access the Internet every day to perform searches, participate in social networking, send and receive e-mails, share pictures and videos, and scores of other applications. Equipped with a growing number of content-generating devices, more information is being created by individuals than by businesses. Information created by individuals gains value when shared with others. Figure 1-1 depicts this virtuous cycle of information. Chapter Objective This chapter describes the evolution of information storage architecture from simple direct-attached models to complex networked topologies. It introduces the information lifecycle management (ILM) strategy, which aligns the information technology (IT) infrastructure with business priorities. 1.1 Information Storage Businesses use data to derive information that is critical to their day-to-day operations. Storage is a repository that enables users to store and retrieve this digital data. 1.1.1 Data Dept. of CSE, JIT,Davangere 2014-15 1

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STORAGE AREA NETWORKS (10CS765) Data is a collection of raw facts from which conclusions may be drawn. Handwritten letters, a printed book, a family photograph, a movie on video tape, printed and duly signed copies of mortgage papers, a bank’s ledgers, and an account holder’s passbooks are all examples of data. The data can be generated using a computer and stored in strings of 0s and 1s, as shown in Figure 1-2. Data in this form is called digital data and is accessible by the user only after it is processed by a computer. The following is a list of some of the factors that have contributed to the growth of digital data: 1. Increase in data processing capabilities: Modern-day computers provide a significant increase in processing and storage capabilities. This enables the conversion of various types of content and media from conventional forms to digital formats. 2. Lower cost of digital storage: Technological advances and decrease in the cost of storage devices have provided low-cost solutions and encouraged the development of less expensive data storage devices. This cost benefit has increased the rate at which data is being generated and stored. 3. Affordable and faster communication technology: The rate of sharing digital data is now much faster than traditional approaches. A handwritten letter may take a week to reach its destination, whereas it only takes a few seconds for an e‑mail message to reach its recipient. The importance and the criticality of data vary with time. Most of the data created holds significance in the short-term but becomes less valuable over time. This governs the type of data storage solutions used. Individuals store data on a variety of storage devices, such as hard disks, CDs, DVDs, or Universal Serial Bus (USB) flash drives. 1.1.2 Types of Data Data can be classified as structured or unstructured (see Figure 1-3) based on how it is stored and managed. Structured data is organized in rows and columns in a rigidly defined format so that applications can retrieve and process it efficiently. Structured data is typically stored using a database management system (DBMS). Data is unstructured if its elements cannot be stored in rows and columns, and is therefore difficult to query and retrieve by business applications. For example, customer contacts may be stored in various forms such as sticky notes, e-mail messages, business cards, or even digital format files such as .doc, .txt, and .pdf. Dept. of CSE, JIT,Davangere 2014-15 2

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STORAGE AREA NETWORKS (10CS765) 1.1.3 Information Information is the intelligence and knowledge derived from data. Data, whether structured or unstructured, does not fulfill any purpose for individuals or businesses unless it is presented in a meaningful form. Businesses need to analyze data for it to be of value. Effective data analysis not only extends its benefits to existing businesses, but also creates the potential for new business opportunities by using the information in creative ways. Example: Job portal. In order to reach a wider set of prospective employers, job seekers post their résumés on various websites offering job search facilities. These websites collect the résumés and post them on centrally accessible locations for prospective employers. In addition, companies post available positions on job search sites. Job-matching software matches keywords from résumés to keywords in job postings. In this manner, the job search engine uses data and turns it into information for employers and job seekers. 1.1.4 Storage Data created by individuals or businesses must be stored so that it is easily accessible for further processing. In a computing environment, devices designed for storing data are termed storage devices or simply storage. Devices such as memory in a cell phone or digital camera, DVDs, CD-ROMs, and hard disks in personal computers are examples. 1.2 Evolution of Storage Technology and Architecture Historically, organizations had centralized computers (mainframe) and information storage devices (tape reels and disk packs) in their data center. The evolution of open systems and the affordability and ease of deployment that they offer made it possible for business units/departments to have their own servers and storage. In earlier implementations of open systems, the storage was typically internal to the server. Originally, there were very limited policies and processes for managing the servers and the data created. To overcome these challenges, storage technology evolved from non-intelligent internal storage to intelligent networked storage (see Figure 1-4). Dept. of CSE, JIT,Davangere 2014-15 3

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STORAGE AREA NETWORKS (10CS765) The technology evolution includes: 1. Redundant Array of Independent Disks (RAID): This technology was developed to address the cost, performance, and availability requirements of data. It continues to evolve today and is used in all storage architectures such as DAS, SAN, and so on. 2. Direct-attached storage (DAS): This type of storage connects directly to a server (host) or a group of servers in a cluster. Storage can be either internal or external to the server. External DAS alleviated the challenges of limited internal storage capacity. 3. Storage area network (SAN): This is a dedicated, high-performance Fibre Channel (FC) network to facilitate block-level communication between servers and storage. Storage is partitioned and assigned to a server for accessing its data. SAN offers scalability, availability, performance, and cost benefits compared to DAS. 4. Network-attached storage (NAS): This is dedicated storage for file serving applications. Unlike a SAN, it connects to an existing communication network (LAN) and provides file access to heterogeneous clients. Because it is purposely built for providing storage to file server applications, it offers higher scalability, availability, performance, and cost benefits compared to general purpose file servers. 5. Internet Protocol SAN (IP-SAN): One of the latest evolutions in storage architecture, IP-SAN is a convergence of technologies used in SAN and NAS. IP-SAN provides block-level communication across a local or wide area network (LAN or WAN), resulting in greater consolidation and availability of data. 1.3 Data Center Infrastructure Organizations maintain data centers to provide centralized data processing capabilities across the enterprise. Data centers store and manage large amounts of mission-critical data. The data center infrastructure includes 1) computers, 2) storage systems, 3) network devices, 4) dedicated power backups, 5) and environmental controls (such as air conditioning and fire suppression). 1.3.1 Core Elements Dept. of CSE, JIT,Davangere 2014-15 4

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