ADVANCED SERVER VIRTUALIZATION VMware and Microsoft Platforms in the Virtual Data center phần 2 pdf

54  Advanced Server Virtualization servers to be backed up in an easier manner helping with disaster recovery.  e lifetime of legacy servers and applications can be signifi cantly extended and the performance increased by moving them to virtual machines. Disaster recovery strategies can be enhanced through the use of server virtualization, which can dramatically reduce the time and complexity required to restore vital systems in the event of a catastrophic event, improving the chances of business continu- ance. Server virtualization can also help reduce the costs involved in creating highly-available systems, also aiding in business continuance through increased fault tolerance. In addition to cost reduction, server virtualization opens up new opportunities by providing the capabilities to easily create adaptive and on-demand computing systems increasing an organization’s productivity. Server virtualization is not the answer to all business problems, however, and some sys- tems do not lend themselves well to be run within virtual machines, including performance-sensitive applications, graphics-intensive applications, and appli- cations requiring specialized hardware. It is important to take these limits into consideration when planning for server consolidation projects, legacy server and application support, disaster recovery, and high availability solutions. All in all, virtualization can save the organization thousands to millions of dollars through more effi cient and eff ective use of hardware. Marshall_AU3931_C004.indd 54Marshall_AU3931_C004.indd 54 3/31/2006 10:55:13 AM3/31/2006 10:55:13 AM 55 Chapter 5 Other Uses of Server Virtualization  is chapter provides soup-to-nuts server virtualization usage scenarios, which build upon the ideas presented in the previous chapter. Practical use cases are presented to show how server virtualization solves problems more easily than traditional approaches.  ese pain points or problems facing organizations cross over into their IT departments. By utilizing virtualization, these departments can learn to solve these problems in a more effi cient manner, saving on both time and cost, and allowing their departments to succeed in areas that would previously cause them productivity problems without answers.  ese depart- ments are made up of the following groups:  Software Development and QA/Testing  Technical Support and Help Desk  Software Training and E-Learning Systems Software Development and QA/Testing Let’s face it; software manufacturing is not getting any easier. On the contrary, it is becoming more and more diffi cult to get a quality software product to market. As the number of operating system choices (along with their hot fi xes, patches, and service packs) continue to increase, the development and testing eff ort to ensure the application performs as expected on each platform becomes exhausting. In addition, today’s applications may also need to support multiple browser versions, various databases, and have strong interoperability with other applications.  e problems compound as software manufacturers are faced with obstacles such as a decreasing budget, the demand for a shorter product life Marshall_AU3931_C005.indd 55Marshall_AU3931_C005.indd 55 3/31/2006 11:01:03 AM3/31/2006 11:01:03 AM 56  Advanced Server Virtualization cycle, and the need to deliver the products to market quickly. Unfortunately in today’s world of software, it is sometimes more important to be the fi rst to market rather than the best. However, time to market and quality of product do not have to be mutually exclusive. In fact, by accepting virtualization as a tool, it can help address the department budget problem, accelerate the development cycle, and improve product quality and productivity. Reduce Budget From a business standpoint, software manufacturers face the challenge of de- livering their product to market at a competitive price. One way to do so is by controlling the budget costs associated with the development and testing orga- nization. Building out a development and QA lab is both expensive and time consuming. Consider the costs associated with a single server: the price of the server itself, rack space, disk space, network gear, cabling, power consumption, cooling, and maintenance costs to name but a few. With a virtualization solu- tion in place, software manufacturers can streamline their resources and not only lower hardware costs but also signifi cantly reduce operation costs.  Hardware expenditures are immediately reduced by 50 to 80 percent.   e cost for multiple desktop machines for each developer goes away.   e need for additional data center or lab space is either delayed or elimi- nated.  Power consumption and cooling costs go down.  Cabling costs and complexity are decreased.  Hardware maintenance and associated management costs from IT are minimized. Virtualization can help reduce hardware expenditures in a number of ways. First and foremost, future purchases of server and desktop equipment can be mini- mized. Because virtualization allows a single machine to be sliced into a number of virtual machines, less hardware needs to be purchased going forward. For example, while a developer may currently have three or four desktop computers at his desk, this can easily be replaced with a single machine running multiple virtual machines. Likewise, a server in a test lab that is currently running one instance of an operating system can be further consolidated into multiple virtual machines. Depending on the horse power of the physical server and the require- ments of the applications, it is not uncommon to get anywhere from a 4 or 12:1 server consolidation ratio. Server consolidation in the test lab alone could save a company millions of dollars on hardware expenditures. Additionally, existing physical equipment found in a development and testing lab is more than likely being underutilized. In a production environment, server equipment is generally running at between 5 and 20 percent utilization. How- Marshall_AU3931_C005.indd 56Marshall_AU3931_C005.indd 56 3/31/2006 11:01:11 AM3/31/2006 11:01:11 AM Other Uses of Server Virtualization  57 ever, in a development and test environment, this is considered idle and wasted server capacity. Virtualization pushes a host server to between 60 and 80 percent utilization, which translates to a successful and properly used test server.  e ag- gregate is that there is a signifi cant reduction in dedicated hardware equipment and an increase in utilization. Finally, server consolidation and an increase in server utilization bring about a natural reduction in the number of physical servers needed in a development and QA lab. Not only does it lower a company’s hardware costs, but it also helps to reduce operational costs.  e lab can now be scaled out in a smoother and more cost eff ective manner. With less physical equipment comes the ad- ditional cost savings of less fl oor space needed, reduced power consumption, less air conditioning required for cooling and even cabling costs and complexity are reduced. And on top of it all, maintenance and management costs are also minimized. A decline in server count yields a signifi cant savings for the IT de- partment.  ey no longer need to order and rack as much equipment and they do not need as many maintenance or support contracts, due to the reduction in equipment needs.  is also allows IT staff to have more time to be responsive to other types of requests made by the development and testing organization. Accelerating Development and Testing Cycle While cutting costs is important, if it takes four years to develop and test a software product, then chances are that boat has already sailed. Software manu- facturers are trying to create a product that meets a need in the marketplace. However, with the rate at which the industry changes, the window to meet that need gets more and more narrow. It is for this reason that software manufactur- ers are searching for solutions to accelerate the development and testing cycles of their products. One such method is found at the core of virtualization: the ability to slice one physical computer into many individual computers. Without this feature, devel- opers must keep multiple computers at their desk in order to properly platform test and unit test their code. Or even worse, if a developer wanted to test their code against two diff erent operating systems and only had one physical machine, they would have to test one operating system all the way through, rebuild the machine, and then test it again all the way through against the second operating system. With virtualization, a developer can greatly increase the development cycle by utilizing multiple virtual images on the same physical computer.  ere is no longer a need to have a cluttered work area with various computer builds or spend the time reimaging, rebuilding, and retesting against the same machine. To help accelerate the testing cycle, virtualization provides another key com- ponent commonly called the undoable disk. Undoable disks make testing in a clean and reproducible test environment almost trivial. In the past, a QA team Marshall_AU3931_C005.indd 57Marshall_AU3931_C005.indd 57 3/31/2006 11:01:11 AM3/31/2006 11:01:11 AM 58  Advanced Server Virtualization would either have to put their faith in the uninstaller program to completely remove all remnants of the application and leave it in a clean state, provide mul- tiple physical machines for parallel testing and spend a lot of valuable testing time rebuilding or reimaging machines. Now, a tester can easily step through a test scenario and at any stage simply power the virtual machine off , discard the changes made and resume from a previous state by leveraging the undoable disk feature that virtualization provides. If a new build or patch is available, the tester simply needs to update the virtual machine, power it off to commit the changes, and then power the virtual machine back on to resume testing.  is is an enor- mous advantage over traditional physical computer solutions. Part of accelerating the product cycle can include virtualization’s ability to help with isolated sandbox testing. Virtualization can provide a “network in a box,” in other words, it can provide virtual machines with isolated virtual network environments. Developers and testers can now create real-world net- working environments without messy cables and without waiting for IT help and approval. Sandbox testing can now easily be accomplished without the fear of compromising the production network environment. Another advantage to using the virtual network, developers and testers can quickly obtain IP addresses without having to bother the network administrator. And best of all, no ad- ditional hardware is needed to quickly test between diff erent operating system environments.  erefore, a virtual machine running Windows XP and Internet Explorer as its Web browser can communicate with a Linux virtual machine running an Apache Web server, all internally to the host server without ever go- ing out onto the physical network. And fi nally, most development and testing organizations are all too familiar with lab ineffi ciency and obscene server provisioning time. It happens all the time, a developer or tester needs a piece of hardware to test part of the product and they have to go through a time consuming process to justify the need. After contacting IT, there is a procurement process involved that includes equipment setup time. When all is said and done, it takes anywhere from fi ve to eight weeks to justify, order and receive, build and rack the server, and then install the software. When done properly with virtualization, this process can take as little as fi ve minutes. Imagine the acceleration of a production cycle when employees can gain control of needed resources within minutes rather than waiting weeks. Improve Product Quality and Productivity In addition to accelerating the development and testing cycle, virtualization can dramatically improve the quality of an application as well as greatly increase the productivity of both the development and test groups. With software applica- tions, the name of the game is getting the application to market as quickly as possible. However, sacrifi cing product quality to be fi rst is not the answer.  e market is littered with applications that “made it fi rst.” But with disregard for Marshall_AU3931_C005.indd 58Marshall_AU3931_C005.indd 58 3/31/2006 11:01:12 AM3/31/2006 11:01:12 AM Other Uses of Server Virtualization  59 product quality, those companies ostracized their customers and ended up losing the race anyway. Virtualization may not be the Holy Grail, but it does provide certain features to help boost product quality and productivity. Virtual machine portability allows the development team and the test team to work together more effi ciently. Now, when the QA group identifi es a bug within the product, it can easily be reproduced by the developer. Instead of the develop- er trying to reproduce the bug on a dissimilar system setup, they can simply use the QA virtual machine exhibiting the problem. Once QA identifi es the bug, the virtual machine can be powered down and the virtual disk fi les can be cop- ied to the developer’s machine. Once the virtual machine is powered back on, the developer can not only quickly see the bug reproduced but then also have a machine to validate any code corrections that are made to resolve the bug. Most virtualization platforms provide an API for software developers to be able to automate routine events. Testing organizations can then leverage these APIs to help with automated testing. Using custom and third-party application testing tools, scripts can be run to control and manipulate virtual machines via APIs in ways that may are not possible on physical servers.  is helps test teams to automate software testing against a high volume of machines and a large number of confi gurations. Finally, virtualization provides a platform for software manufacturers to cre- ate a standardized development and testing environment.  e diffi cult process of confi guring hardware and installing software every time a new environment is needed can fi nally be eliminated. By performing the setup once for each en- vironment type, a library of template images is created (see Figure 5.1).  ese Windows 2000 SP4 Location 1 Template Library Shared Access Location 2 Location 3 Red Hat Linux Windows XP SP2 Windows 2003 SP1 Windows NT 4 SP6 Windows 2000 Pro Figure 5.1 Template Library. Marshall_AU3931_C005.indd 59Marshall_AU3931_C005.indd 59 3/31/2006 11:01:12 AM3/31/2006 11:01:12 AM 60  Advanced Server Virtualization virtual machine template images ensure a consistent environment is created no matter who sets it up. It also greatly enhances the quality of a product and the productivity of an organization because developers can now spend more time writing and testing code and less time building and rebuilding environments.  e consistency and speed at which these template environments are built also greatly enhance project quality in the QA department. Test groups can now pro- vide more rigorous testing, testing more diverse environments in less time than before. Template images can be created with diff erent operating systems, various browsers and multiple languages. As quickly as template images can be rolled out, the QA department can instantly create an entire test bank for regression testing. With more time spent testing the product and less time building the environments, the quality of the product becomes that much greater. Take the following scenario as an example: A testing organization is tasked with testing a multi-tier Web application.  e application requires a database back-end, either Microsoft SQL Server or Oracle Database.  e Web applica- tion can be installed on Windows 2000 Server, Windows 2003 Server, or Red Hat Enterprise Linux.  e Web application also requires either IIS or Apache be installed. And fi nally, the Web application offi cially supports either Microsoft IE 5.5, 6.0, or Mozilla Firefox 1.0.  e testing matrix in this example can become daunting when using physical equipment. Imagine needing a physical server for every possible combination. At fi rst, it may not seem to be that cumbersome. However, when you start adding up the number of service packs and hot fi xes alone for each operating system, database, and browser, the list grows exponentially.  en, when an indi- vidual tester runs through one test iteration and either hits a road block or makes it through to the end, what happens next?  ey need to clean off the system by uninstalling, reimaging, or rebuilding the server so they can perform the next test or perform the same test over.  e time it takes between tests in a physical lab environment is so long, it is a wonder that any software product ever makes it to market. Now consider running the same tests against a virtual environment leverag- ing a library of template images and the toolset found within the virtualiza- tion platform.  is same test matrix can be accomplished with a fraction of the equipment and in a fraction of the time. A template of each environment build can be created and stored, allowing templates to be brought on and offl ine at will.  erefore, a Windows 2000 Server virtual machine can be created, a copy of the virtual hard disk fi le can be saved, then updated with Service Pack 1, and saved again and so on, rather than starting from a barebones state each time. In the end, these template images can be rolled out and plugged together in a virtual network within a matter of minutes. If a test fails, the virtual machine can be rolled back to a previous state and the test can continue just as soon as the machine is powered back on. With this scenario, months of test time can be Marshall_AU3931_C005.indd 60Marshall_AU3931_C005.indd 60 3/31/2006 11:01:13 AM3/31/2006 11:01:13 AM Other Uses of Server Virtualization  61 saved and the product can be released to market much more quickly and with a higher degree of quality. While virtualization does solve many of the problems facing software develop- ment and testing organizations, it does not fi t well when performing performance testing or testing software that interacts with proprietary hardware devices. With virtualization, the resources that are being consumed on the physical machine make true performance testing of an application next to impossible.  e virtual machine is sharing its hardware resources with other virtual machines running, the host operating system as well as the virtualization application itself. While the resources are being mapped out and distributed to the virtual machines, there is a performance hit being taken, which will cause an inaccurate view for performance testing of an application. It is therefore suggested that for this type of testing, a dedicated physical server or group of physical servers be used.  e only exception to this rule, being if the application is planned to be run inside of a virtual machine as the production environment. When the software being tested must interact with nonstandard hardware devices, such as PCI cards, it must be tested on physical hardware. At the pres- ent time, virtualization platforms are limited in the way physical hardware of the host server is mapped as virtual hardware to virtual machines.  e available virtualization platforms are currently closed systems in regards to third-party virtual hardware devices.  is limitation could be overcome in the future if the manufacturers of the virtualization platforms decide to open their systems to al- low third-party virtual hardware devices.  is would allow third parties to write their own virtual hardware to map proprietary hardware devices into a virtual machine. Some hardware devices may be mapped into a virtual machine through the use of parallel, serial, or USB ports, such as security dongles or keys. Technical Support and Help Desk  ere is a buzz today that is focused on a company’s call center or technical support department. Companies are making the claim that they are commit- ted to customer satisfaction and customer service; however, they are faced with increased customer expectations while at the same time faced with a decrease in annual budget.  is dilemma usually causes confusion and frustration for those people answering the customer’s calls, namely the support team. By giving the support team the proper tools to do their job, their frustration level goes down and their productivity goes up, this supports better customer service and a hap- pier support team.  e current trend for most company’s support shops is cost reduction, in- creased effi ciencies and eff ectiveness, and making the most of their current investments. To that end, server virtualization is going to become a huge key factor for running a highly successful technical support shop. By utilizing server Marshall_AU3931_C005.indd 61Marshall_AU3931_C005.indd 61 3/31/2006 11:01:13 AM3/31/2006 11:01:13 AM 62  Advanced Server Virtualization virtualization, a technical support team can reduce the amount of time spent per call, narrow down the complex problems faster to improve response time, and decrease the overall support costs to the company. By adding server virtualiza- tion to the list of tools available to supporting customer problems, the complex problems that may have taken days or weeks to identify and resolve may now be able to be answered within a fraction of the time. In addition to saving response time, server virtualization can also help with budget problems. From a budget standpoint, it is nearly impossible for a technical support group to have enough equipment to match every possible problem/situational matrix.  is matrix can be broken down into various types of hardware and soft- ware confi gurations. On the hardware matrix, does the computer have SCSI or IDE drives? Does the computer have a CD-ROM or multiple CD-ROM drives? On the software matrix, what operating system is running on the computer? What service packs or hot fi xes are currently installed? What version of the ap- plication is running? What other applications are running on the computer? In order to reduce hardware and lab maintenance costs, companies currently combat this problem in a number of ways. For example, a company may pro- vide its support staff with multiple machines, each allowing them to multi boot to various operating systems. Unfortunately, this takes time in both the initial setup and the rebooting involved during calls. It also does not come close to fulfi lling the potentially large matrix involved. It is also possible that the hard- ware available is not suitable for part of the matrix. Perhaps the hardware of the computer does not allow Microsoft Windows NT or Red Hat Linux to install. Others may choose to have an even smaller subset of computer equipment avail- able, but have a library of multiple images available, such as Symantec Ghost images. Again, both initial setup and imaging can take a very long time. Once a support call comes into the call center and the technical support specialist determines the caller’s setup, it may take hours to reconfi gure a machine with the proper image and software before troubleshooting can even begin. Finally, another choice some shops are forced to take is by working through the problem by memory and experience.  e technical support specialist may try to walk the caller through diff erent application or operating system screens purely by memory, also known as fl ying by the seat of your pants. Server virtualization solves many of these problems. Obviously, if a company could staff an on-site technical support specialist at each customer’s location, the effi ciency and eff ectiveness of technical sup- port would be through the roof, unfortunately, so would the cost. By utilizing server virtualization, a technical support group can also increase their effi ciency and eff ectiveness, as well as keep the costs down. To combat the overwhelming matrix, server virtualization can minimize the amount of computer hardware and lab resources needed to cover most of the possible hardware and software combinations. Within a virtual machine, it is relatively easy to quickly modify certain hardware confi gurations. A technical support specialist could quickly Marshall_AU3931_C005.indd 62Marshall_AU3931_C005.indd 62 3/31/2006 11:01:13 AM3/31/2006 11:01:13 AM Other Uses of Server Virtualization  63 change the amount of ram, the disk drive type, the CD-ROM confi guration, or even whether or not the virtual machine has a serial port. On the software con- fi guration side of the matrix, a call center can house a library of confi gurations on a local fi le server.  ese software confi gurations can then be used to quickly replicate a caller’s computing environment. For example, when a call comes in, the technical support specialist can fi nd out what hardware confi guration is be- ing used, what operating system is running, what service pack, patch level, or build version is being used, what application version is installed, etc. A virtual machine image with a matching confi guration can then be copied over to the host server and powered on, or if the image already exists on the host server, it can be started from a saved state.  is would allow the technical support spe- cialist to start troubleshooting and diagnosing the problem for the caller within minutes of answering the phone. All of this could be accomplished with just one physical server per technical support specialist or one physical server shared across a team. It is also possible for a call center to get a near replica of a customer’s server for troubleshooting purposes. As server virtualization makes its way across the IT industry, it will become more and more commonplace for customers to in- stall their applications within a virtual machine. If the machine in question is a virtual machine, the caller can either shutdown the machine in question or use a backup copy of that machine’s disk fi le and send a copy to the call center for troubleshooting. If the machine cannot be down for a long period of time, it can be suspended or put into a saved state. Once in this state, it can be quickly copied and resumed or restored. If the customer is not using virtualization, one of many methods of physical to virtual (P2V) conversions can be used to make a virtual machine from the problem physical server.  is is undoubtedly one of the better ways to troubleshoot a customer’s machine without having to be there locally and also having the ability to make changes without aff ecting a produc- tion machine. Virtualization also allows the technical support specialist to always start with a clean operating system environment. It is important to know when trouble- shooting a problem that the starting point is clean, in good working order, and has not been touched by anyone else inside or outside of the team. As stated briefl y in chapter 3, these clean starting points can be used over and over again by using a virtualization process known as undo disks. If during the trouble- shooting process a machine crashes or blue screens, the technical support spe- cialist can simply discard the changes made during troubleshooting and resume troubleshooting from the original clean starting point within minutes.  e dif- ference between discarding the changes in a virtual machine and reinstalling or reimaging a physical server could be the diff erence between helping the cus- tomer and helping the customer choose a new vendor. In addition to confi guration changes, server virtualization will also help a call center with easy network isolation during troubleshooting.  is is important for Marshall_AU3931_C005.indd 63Marshall_AU3931_C005.indd 63 3/31/2006 11:01:13 AM3/31/2006 11:01:13 AM [...]... Microsoft Windows 98 Microsoft Windows Millennium Edition Y Y Y Microsoft Virtual Server R2 VMware ESX Server 2. 5 .2 VMware GSX Server 3 .2. 1 Y Y Y Guest Operating System Microsoft Microsoft Wndows Wndows Server 20 03 Server 20 03 R2 RTM, SP1 Virtualization Platform Microsoft Windows NT 4.0 Server SP6a Microsoft Windows 20 00 Microsoft Windows XP Microsoft Virtual Server R2 Y Y Y Y VMware ESX Server 2. 5 .2 Y Y... VMware GSX Server 3 .2. 1 Y Y Y Y Microsoft Wndows Vista Beta Y Y Guest Operating System Virtualization Platform Red Hat Red Hat Linux Linux 6 .2, 7.0, 7.1 7 .2, 7.3, 8, 9 Red Hat Enterprise Linux 2. 1, 3.0 Red Hat Enterprise Linux 4.0 SUSE Linux SUSE Linux Enterprise Enterprise Server Server 8, 9 7 Microsoft Virtual Server R2 VMware ESX Server 2. 5 .2 VMware GSX Server 3 .2. 1 Y Y Y Y Y Y Y Y Y Mandrake Linux... machine The operating system and virtualization platform installed on each host server defines the overall environment in which the virtual machines will reside Together, they set the initial boundaries of the environment by their supported capabilities and features For example, if each host server will have Microsoft Windows Server 20 03 Standard Edition as its operating system and Microsoft Virtual Server. .. 8.0, 8.1, 8 .2 Mandrake Linux 9.0, 9.1, 9 .2 Mandrake Linux 10.0, 10.1 Y Y Y Solaris x86 9, 10 Turbolinux 7, ES 8, WS 8 Y Y Guest Operating System Virtualization Platform SUSE Linux SUSE Linux SUSE Linux 8 .2, 9.0, 7.3, 8.0, 9.3 9.1, 9 .2 8.1 Microsoft Virtual Server R2 VMware ESX Server 2. 5 .2 VMware GSX Server 3 .2. 1 Y Y Y Y Guest Operating System Virtualization Platform FreeBSD 4.9, 5.0, 5 .2 Figure 6.1... such as Virtual Machine Remote Control in MSVS and the VMware Remote Console in ESX Server and GSX Server This is primarily due to the lack of optimized keyboard, Marshall_AU3931_C006.indd 81 4/13 /20 06 11:30: 12 AM 82 Advanced Server Virtualization Guest Operating System Virtualization Platform Microsoft DOS (MS-DOS) Microsoft Windows for Microsoft Windows 3.1 Workgroups 3.11 Microsoft Windows 95 Microsoft. .. NetWare 4 .2 Server Novell NetWare 5.1, 6.0, 6.5 Server Microsoft Virtual Server R2 VMware ESX Server 2. 5 .2 VMware GSX Server 3 .2. 1 Y Y Y Y Y Supported Guest Operating Systems by Server Virtualization Platform Marshall_AU3931_C006.indd 82 4/13 /20 06 11:30: 12 AM Planning for Deployment 83 mouse, and video drivers in the guest operating system usually supplied by the guest enhancement software package In this... for most of the common problems that software trainers battle daily The benefits that server virtualization brings to the software training and E-learning space are enormous, both in time and cost savings Software training organizations are constantly looking for ways to improve the student experience in their classrooms and to increase the quality of instruction by their staff Through server virtualization, ... understanding of the project is required This understanding is realized by learning the issues and considerations specific to server virtualization, defining the use case, obtaining the specific requirements, and planning the deployment By taking the time to properly plan and document the project, the implementation will have a much higher degree of success and less risk This chapter covers many server virtualization. .. virtualization platforms may be one of the most common starting points in the decision making process But testing the software in house is one of the best, more objective methods This discussion will focus on the three major server virtualization platforms available today: Microsoft Virtual Server (MSVS), VMware GSX Server, and VMware ESX Server 69 Marshall_AU3931_C006.indd 69 4/13 /20 06 11:30:10 AM 70 Advanced Server. .. being faced and they are eating away at company resources Trainers are confronted with the following Marshall_AU3931_C005.indd 64 3/31 /20 06 11:01:14 AM Other Uses of Server Virtualization 65 problems on a regular basis and each can be solved through the use of server virtualization: Updating labs and course scenarios Dealing with variations in student machines inside of single classrooms Installing and . discard the changes made during troubleshooting and resume troubleshooting from the original clean starting point within minutes.  e dif- ference between discarding the changes in a virtual machine. understanding of the project is required.  is understanding is realized by learning the issues and considerations specifi c to server virtualization, defi ning the use case, obtaining the specifi. it through server virtualiza- tion and classroom cloning. Whether a corporate training center, university, technical vocational institution, or an in- house training group, server virtualization