The Essential Guide to Storage Area Networks
Authors: John R. Vacca
Venue:  (2001)

From the Book:IntroductionThe increasingly sophisticated and prolific world of IT has dramatically altered the demand for data storage and enhanced its value to the enterprise. Desktop, department, and enterprise environments have all evolved to the point where data that was once viewed as a static resource is now viewed as a mission-critical company asset. In this highly competitive environment, the IT community has come to realize how the capabilities of online storage management and the presence of a standard operating system such as Windows NT can significantly enhance data storage systems.At the desktop level, office applications such as spreadsheets, word processors, database programs, multimedia, and imaging software have driven the most recent generation of PCs to the point where they feature hard drives with multiple gigabytes of storage and random access memory (RAM) of up to 1 gigabyte. Moving up to the department and workgroup levels, the demands on data storage have increased exponentially as users have begun working collaboratively on projects that generate terabytes of data and span not only departments and workgroups, but nations and continents.Importance of StorageStorage was once a peripherala mere feature of the server. Those days are long gone, and that's a good thing because information shouldn't always be hidden behind, or bottled up inside, a single server. It should be positioned so that it can be made quickly but securely available to other applications and/or departments within the enterprise. So, now that storage is out from behind the server's shadow, we need to recognize its true value. Here's why: First, thevalue of data as a corporate asset has risen dramatically over the last few years. Maintaining its availability, integrity, and security is now a matter of life or death for many enterprises.Second, with the advent of storage networking, data storage as an enterprise core competency has become demanding and complex. And with new technologies reaching the market at a torrid pace, it becomes harder and harder to understand and make judgments about all the alternatives.Finally, there is currently a critical shortage of the trained staff required to manage the new enterprise storage environment. As a result, expertise in recruiting, training, and retaining storage management staff is now a vital enterprise IT function.Value of DataData (translated by applications and infrastructure into information) has grown in value to the point where, for many enterprises, it is the most valuable corporate asset. It's a competitive differentiatorthe underpinning of all customer-facing applications like CRM and CSM. And with the advent of the Web, it has expanded in importance to become mission-critical to the very enterprise as viewed through the portal. In this environment, storage is now the single most important IT resource for assuring: Data Availability Data Integrity Disaster RecoverabilityData AvailabilityThe persistent availability of data as defined by the storage utility model which basically assures that enterprise data will always be accessible, will always be onjust like electricity. Lost access to data can be severely damaging and possibly fatal to the enterprise. For example, in a health c setting, continuous access to data could make the difference between life and death.Data IntegrityThe protection and preservation of data from corruption, loss, and outside attack is known as data integrity. Storage can also be thought of as a vault. When you retrieve data, you expect to retrieve exactly what was deposited. Storage and storage management personnel are the guardians of data.Disaster RecoverabilityThe ability of storage networks and storage management applications to play a critical role in recovering from the inevitable disaster is known as disaster recoverability. Disaster scenarios include anything from the loss of a server running a critical application, to the loss of an entire data center due to fire, flood, earthquake, etc.Enterprise Core CompetencyIt would be a gross oversimplification to say that storage was once a simple matter of plugging an array into a SCSI port. Then again, compared to the array of alternatives available now from FC-AL to FC Fabric, the IP derivatives and soon InfiniBand and beyond, the days of one-size-fits-all SCSI are also long gone. Data storage as an enterprise core competency is becoming exceeding complex. Here's a brief, and by no means exhaustive, list of the technologies now directly involved in or significantly touching upon data storage as covered in this book: Fibre Channel-Arbitrated Loop and fabric architectures Ethernet and IP Server clustering Data backup and restoration SCSI Wide and Metropolitan Area Networking protocols Bridging, routing, and switching Host bus adapters and driver communications Enterprise management applications Database and file system architectures Operating systemsPros and Cons of Storage As companies grapple to store and protect vast (and growing) amounts of data, Storage Area Networks (SAN) are gaining momentum. A SAN is a dedicated configuration of multiple servers connected to peripheral storage devices using high-speed fiber and special routers, switches, and hubs. A SAN, usually part of an enterprise's overall computing resources, enables enterprises to consolidate data from disparate servers onto a centrally managed storage network.Storage Area Networks offer certain key advantages over file serving and Network Attached Storage (NAS) boxes, namely improved data sharing, convenient storage expansion, remote backup and recovery, and increased uptime. But the adoption rate of SANs has been slowed by drawbacks such as high cost; interoperability of software; hardware and components; and data security concerns.The ProsSome companies see Storage Area Networks as a solution. The following are the pros: Data sharing Live expansion capacity Remote backup and recoveryData SharingA SAN makes stored data available to multiple users simultaneously, without disrupting productivity. A SAN provides high-speed access to data among a number of system servers, thus enabling data to be retrieved faster when used by a large number of users. This is critical for efficient company operations and for Web storage where millions of users may need to access data.Individual computers in a SAN see each data resource, eliminating data bottlenecks common to NAS and file serving environments. You might have 30 computers, but each one sees the storage as one big pool.Live Expansion CapacityA SAN allows network administrators to expand storage capacity without shutting down critical file servers. Instead, new storage devices are plugged directly into the fiber connecting the various servers to existing storage capacity. With the Internet, system administrators have to make sure their data is available all the time-and keep it safe to boot.Remote Backup and RecoverySince it's a separate network, a SAN enables automatic data backup, meaning IT administrators don't need to swap out backup tapes each day. Backup occurs without interrupting users on other company computer networks. One of the complaints of companies using NAS boxes is that backup traffic is consuming too much bandwidth from their production networks.A SAN also makes data migration more manageable. Data is transported across high-speed fiber and stored on a remote server. This eliminates the need to store data on the hard drive of individual machines. It also makes data recovery easier if there's a disaster.The ConsThe information age presents network managers with a daunting challenge: store ever-increasing amounts of business-critical data, keep it secure but accessible at high speeds to multiple users, and ensure timely, regular backupall without increasing IT costs. The following are the cons: Cost Interoperability Network SecurityCostIndustry experts say a comprehensive SAN could cost hundreds of thousands of dolla putting them beyond the reach of most small enterprises. Although a SAN could yield savings through the need for fewer IT professionals, the upfront cost intimidates most companies.Some small- and medium-size enterprises might want to build miniature SANs, consisting of a few switches on the network, for specific departments and applications. These smaller networks give them a head start and can be expanded later to accommodate their computing needs.InteroperabilityInteroperability also is a drawback. Companies implementing a SAN often buy hardware from one company, software from another company, while a third company supplies the components needed to connect everything together. There is no overarching standard for SANs right now. A lot of vendors make a single component, so companies need to be careful that the components they select are compatible with their system.The Storage Networking Industry Association (SNIA) of Mountain View, California, is promoting open standards to ensure that different vendors' storage networking products work compatibly. But the association concedes open standards are at least a year or two away.Network SecurityThe lack of industry standards also heightens concern about security and the ability to prevent unauthorized access to data. Several workable options exist, including hybrid systems that use newer technology with more established architectures. Concern about security is the chief impediment to widespread implementation of SANs.Security safeguards should be built into a SAN. A SAN really is no different than any other computer network. The same need to separate different kinds of machines so that they can't be used to leverage each other's access still exists.Multiple Data Storage Options The question for today's enterprise then, is how to manage the myriad aspects of storing and controlling this data in all of its new forms across not only the local and departmental levels, but also the divisional and corporate levels. The most obvious facet of this question is the quantity of data which must be managed and its storage requirement. However, simply providing enough storage capacity is not sufficient. Organizations today must also worry about the performance of the devices relative to the needs of the users, the cost-per-megabyte of that storage, the reliability of the different devices (which directly relates to the concept of system availability), and the ease with which an organization can ensure that data read from the storage media is identical to that written (data integrity). Different storage devices have different profiles in terms of the dimensions described in the preceding. Some are slower but cheaper, some have very high capacity but are expensive, and so on. Users, too, have different needs in terms of these same dimensions, so most enterprises today attempt to mix and match the technologies and their profiles to the specific needs of their users and their corporate bottom lines.Planning for and architecting an online storage management approach has become a required exercise in prudent IT operations. A good online storage management plan is one that understands user profiles and makes use of the various storage alternatives. This sound approach will avoid the traps many organizations fall into, where the misapplication of technology to a storage need results in overly expensive solutions, poorly performing solutions, and, almost always, in dissatisfied customers.Not surprisingly, storage technology is typically categorized according to the different profile dimensions described earlier: availability, capacity, performance, and economics. The availability of data is directly related to its logical location. Online data is immediately available to users. Nearline data is a term that applies to data accessible to the user after a noticeable delay, but which is still completely automated by the storage device. Because it is either no longer available or has been archived to lower-cost media, offline data (sometimes referred to as farline data) is typically housed in libraries not connected to any storage device, and which must be manually handled and mounted on the device in order to be delivered to the user. Tape libraries are good examples of offline or farline storage. In developing software systems, there is an old joke that goes One can get software systems built that are good, fast, or cheap; pick any two. Similarly, there are tradeoffs in the combinations of attributes of different systems. You can get high capacity and fast access time only at very expensive prices; you can get lower prices by sacrificing either access time or capacity, and so on.A well-conceived online storage management system optimizes all three of these data storage categories by automatically ensuring that they each contain prioritized data available at access speeds that correlate to the data's value. This approach requires that the most frequently used data be stored on magnetic disks and available online, while less active data is maintained in nearline mode on optical disks or tape. This logical approach to prioritizing and accessing data streamlines business processes and maximizes the productivity of users, while controlling the costs of storage.Managing the Arsenal The good news is that there is an arsenal of storage devices that can be deployed in response to an organization's needs. In fact, most organizations typically rely on a variety of storage devices in order to satisfy all of their needs. Optical drives, jukeboxes, fixed and removable magnetic disks, tape drives, and RAID (Redundant Arrays of Independent Disks) are all deployed in varying configurations across enterprises today. The bad news is that you now have to manage a set of repositories that have very different physical and operational characteristics, and your core computer systems don't do nearly as much as you'd like them to do with regards to managing all of this.While some other operating systems, such as UNIX, support the concept of removable devices in the core operating system, PCs and PC-based servers have implemented a storage model that presumes a single platter per drive. Device drivers are used to associate the physical devices to the operating system functions, but as long as the operating system itself only issues commands based on the notion of fixed media, additional software is needed to circumvent this problem. Therefore, any device that features removable or replaceable media, such as the popular Iomega series of drives, the newer optical 120 MB floppy media, or the older Bernoulli boxes, may be physically attached to a computer system, and the operating system will be able to identify it by a letter of the alphabet. If you can assume a system in which there are two floppy drives and two logical partitions of hard drives, the new removable drive might be referred to as drive "E." The operating system will therefore recognize the fact that there is a storage device, but since it assumes that the device is a fixed drive, it will be unaware that the drive is capable of accommodating removable media and, as such, has no mechanism for dealing with multiple, disparate volumes. Therefore, a different and supplementary set of software is needed to help applications recognize the insertion and extraction of removable media. To avoid attempts to write to a device whose media has been changed or removed, ancillary layers of software are designed to impart the concept of volumes, allowing applications to work with removable media even if the application sees each drive as a fixed device.There are three dimensions to the problem of optimizing the plethora of storage media and technologies available on the market today. First and foremost is integrity of the stored information. The system is expected to help the user maintain that integrity through functions such as backup and restore, and the use of cyclic redundancy checks, error correcting codes, or parity checks to make sure the data is not corrupted.Secondly, the system must help the user track and locate where the data is in logical terms and map that location to the physical devices. This entails the management of sectors and tracks on different media and the logical and methodical layout of the data across those sectors and tracks, including correlating those physical locations to a hierarchical or network filing system devised by the users. Finally, you have to be able to handle the multiple technologies used in data management, including optical, magnetic, disk, tape, and so forth.Growing Storage Staff There are benefits to be realized today from implementing storage networks, but because of the shortage of IT personnel with storage expertise, enterprises are hesitant to move forward. Recruiting, training, and retaining skilled storage management staff must become a core IT competency if the real benefits from storage innovation are to be realized.Who's Using SANs? Despite the economies of scale they offer, cost and technical complexity have kept adoption rates of SANs low. It is estimated only 6 to 11% of Fortune 500 companies have installed SANs. The rate among smaller and medium-size enterprises is much lower. In a few years, however, SANs could become a necessity for all organizations with growing data storage demands, especially given the projected growth of e-commerce.Before SANs, the choice was to add more storage capacity to a single server. But no longer it is enough to throw more space at a storage problem. The key is to manage space more effectively, because the one thing companies can't afford to be is down.Finally, the nature of the storage environment has changed radically in the last few years. It is now characterized by unprecedented growth in the volume of data to be managed; a quantum leap in complexity; and the sheer number of available combinations and permutations. Add to that the growing value of data to the enterprise, and the overwhelming importance of storagestorage networking becomes obvious.Who This Book Is for can be used by domestic and international system administrators, government computer security officials, network administrators, senior managers, engineers, sales engineers, marketing staff, WWW developers, military senior top brass, network designers and technicians, SAN project managers, SAN installers, LAN and PBX administrators, and other SAN personnel. This book is also valuable for systems analysts, design engineers, programmers, technical managers, and all dataprocessing, telecommunications, and office automation professionals involved in designing, configuring, or implementing SANs. In short, the book is targeted for all types of people and organizations around the globe who have responsibility for managing and maintaining the SAN service continuity of organizational systems including line and project managers; team members, consultants; software and security engineers; and other IT professionals who manage SAN cost justification, investments, and standards. Others who may find it useful are scientists, engineers, educators, top-level executives, information technology and department managers, technical staff, and the more than 900 million Internet, intranet, and extranet users around the world. Some previous experience with SAN installation is required. What's So Special About This Book? The Essential Guide to Storage Area Networks (SANs) is unique in its comprehensive coverage of SAN installation, cost justification and investments, and the latest standards. The book is a thorough, up-to-the-minute professional's guide to every aspect of SAN and disaster recovery, from planning through installation and management. The high availability of mission-critical systems and communications is a major requirement for the viability of the modern organization. A SAN disaster could negate the capability of the organization to provide uninterrupted service to its internal and external customers. Furthermore, the proliferation of powerful workstations and PCs, together with a vast installed base of minicomputers and mainframes, has produced immense pressure to link these resources. Local Area Networks allow the sharing of programs, data, and peripherals by providing common access to local and remote SAN resources. This book provides you with the fundamental knowledge you need to design, configure, and implement SANs. The book emphasizes the integration of available software and hardware. In this book, you also learn to identify vulnerabilities and implement appropriate countermeasures to prevent and mitigate failure risks. You learn techniques for creating a continuity plan and the methodology for building a SAN infrastructure that supports its effective implementation. Key features include, but are not limited to: Understanding basic SAN terminology, technology, and protocols Selecting SAN technology based on application requirements Configuring SANs to help interconnect the computing resources of your organization Supporting LAN storage Creating, documenting, and testing a successful SAN and disaster recovery plan for your organization Performing a risk analysis and Business Impact Assessment (BIA) to identify vulnerabilities in core processes Selecting and deploying an alternate SAN site for processing mission-critical applications Recovering S infrastructure, systems, networks, data, and user access Organizing and managing SAN and disaster recovery teams Testing and maintaining an effective recovery plan in a rapidly changing IT environment Performing threat and impact analysis Selecting alternative SAN and disaster recovery (DR) sites and equipment Planning your SAN and DR project Developing strategies for SAN systems and communications recovery Organizing team structures for use in an emergency Creating a SAN and disaster recovery plan from an existing templateThe book is organized into seven parts and includes appendixes as well as an extensive glossary of SAN terms and acronyms at the back. It provides a step-by-step approach to everything you need to know about SANs as well as information about many topics relevant to the planning, design, and implementation of them. The book gives an in-depth overview of the latest structured SAN technology and emerging open standards. It discusses what background work needs to be done, such as developing a SAN technology plan, and shows how to develop SAN plans for organizations and educational institutions. More importantly, this book shows how to install a SAN system, along with the techniques used to test the system, as well as the certification of system performance. It covers many of the common pieces of SAN equipment used in the maintenance of the system, as well as the ongoing maintenance issues. The book concludes with a discussion about future planning, standards development, and the SAN industry.Part I: Overview of SANs TechnologyThis part of the b systems software and hardware; the driving forces behind SAN; SAN market demand and projections; the evolution of the SAN market; and the value of information. Next, it discusses disaster recovery; I/O performance; high scalability and flexibility; technology platform, techniques, and alternatives; breaking tradition in video distribution; and SAP R/3 storage management. Part I also covers evolving standards for SANs and SANs standard organizations. Furthermore, this part discusses self-service SAN, outsourcing with service providers, high-speed data sharing among multiple computer platforms; Storage Area Networks: opportunity for the indirect channel, end-to-end services for multivendor enterprise Storage Area Networks and storage subsystems for video services. Finally, this part shows you how to reduce or eliminate single points of failure in enterprise environmentsStorage Area Networks (SANs) can help improve the overall availability of business applications. High availability is achieved not through a single product, but rather through a comprehensive system design that includes all the components in the SAN. By utilizing highly available components and solutions (as well as a fault-tolerant design), enterprises can achieve the availability needed to support 24 X 7 uptime requirements.Part II: Designing SANsPart II begins by giving you an overview of how to design Storage Networks with Fibre Channel switches, switching hubs, and hubs; components; installation planning, and practices; application testing and SAN certification design issues; and SAN design documentation issues. This part covers the financial impact of a SAN, justification of SAN operating costs, and financial considerations and acquisitions. It also shows you how to design distributed SAN standards and discusses new standards design issues. Finally, Part II discusses traditional captive storage architecture, SAN architecture, and SAN design considerations.Part III: Planning for SANsPart III opens up by showing you how to make SANs a reality in your environment with your infrastructure; why Internet-based exchange pours resources into a SAN infrastructure; and how to prepare for a Storage Area Network. Next, Part III shows how SAN clustering technologies are an essential component of this new era of mission-critical web-based commerce. It also shows why sole reliance on industry-standard benchmarks for selecting the right hardware can be detrimental to the SAN architecture design. Finally, you'll learn how SAN simulation techniques can be used to understand the impact of your users, networks, and applications on the clustering requirements to ensure that your virtual doors are never closed.Part IV: Installing and Deploying SANsPart IV discusses physical layer testing, application layer testing, management layer testing, why you should use SAN Testing, and the SANmark Revision TestSuite. This part shows you how to deploy a SAN, get started on a SAN, use storage switch technology to accelerate the next phase of SAN deployment, and put data to work for e-businesses. Finally, this part covers SAN testing and troubleshooting; documenting and testing SANs; and certifying SAN performance.Part V: Maintaining SANsThis part begins by taking a look at the data management solution, virtual Storage Area Networks, and a management strategy for the Fibre Channel-Arbitrated Loop. This part discusses the facts about SAN software; documentation standards; and increasing efficiency in the prepress market. Finally, this part covers present and future SAN management standards.Part VI: SAN Solutions and Future DirectionsOpening up with a discussion on the causes of data unavailability, cost tradeoffs, high availability objectives, and the SAN-including the single building, campus cluster, and metro cluster-this part examines solutions to making SAN work. This part also examines the role of SANs in computer forensics with regards to computer and data storage of evidence collection and forensic analysis. Finally, this part presents a summary, current conclusions, and recommendations for the future of SAN development and implementation.Part VII: AppendicesSeven appendices provide direction to additional resources available for SANs. Appendix A is an online storage management checklist. Appendix B is a list of top SANs implementation and deployment companies. Appendix C contains SAN product offerings. Appendix D consists of standards for SANs. Appendix E is a discussion of SCSI versus Fibre Channel Storage. Appendix F is a list of miscellaneous SAN resources; and, Appendix G is a glossary of SAN terms and acronyms.