Figure 1.1 Two Under-utilized Systems in Software Integrate Code 128 in Software Figure 1.1 Two Under-utilized Systems

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Figure 1.1 Two Under-utilized Systems generate, create barcode standards 128 none in software projects Microsoft Official Website It is possible and often de Software code 128c sirable to run another workload on that same system instead of purchasing a second computer for the second workload. Figure 1.2.

1 . Introduction to Virtualization shows the CPU consumption o f the same two workloads after consolidation onto one system. The amount of wasted investment has decreased by an entire CPU.1 Of course, these examples use average values, and real-world computers do not run well at 100% CPU utilization.

You must also avoid being overly aggressive when consolidating workloads.. Figure 1.2 A Consolidated System In the early days of the co mputer industry, all computers were so expensive that a corporation might be able to own only one. Given the precious nature of this resource, it was important for an organization to make the most of a computer by keeping it as busy as possible doing useful work. At rst, computers could run only one program at a time.

This arrangement was unwieldy when a group of users sought to use the same computer, creating a need for a multiuser operating system. Software engineers designed such operating systems with features that prevented one program from affecting another program in a harmful way and prevented one user from causing harm to the other users programs and data. Other features were designed to prevent one program from consuming more system resources CPU cycles, physical memory (RAM), or network bandwidth than it should.

Later, computer manufacturers developed inexpensive microcomputers, which were easier to afford than relatively expensive minicomputers. Unfortunately, these microcomputers and their early operating systems were not well suited to run multiple production applications. This led to a common practice of running one application per computer.

More recently, progress in computer performance has led to a desirable problem: too much compute capacity. Many servers in data centers run at an average. 1. The OS will spend some c Software Code 128 Code Set A ompute cycles managing resource usage of the two workloads and reducing the impact that one workload has on the other. This mediation increases CPU utilization, thereby reducing available CPU capacity, but we will ignore this effect for now.

. 1.1 DEFINITIONS AND MOTIVATIONS CPU utilization near 10%. M barcode 128 for None any people would like to use most of the rest of this capacity, which can be achieved by consolidating workloads..

1.1.3 Why Is Virtualization so Important for Consolidating Workloads Operating systems designed code128b for None for use by multiple users (e.g., most UNIX derivatives) have a long history of running multiple applications simultaneously.

These operating systems include sophisticated features that isolate running programs, preventing them from interfering with one another and attempting to provide each program with its fair share of system resources. Even these systems have limitations, however. For example, the application might assume that only one instance of that application will be running on the system, and it might acquire exclusive access to a singular, non-shareable system resource, such as a lock le with a xed name.

The rst instance of such an application locks the le to ensure that it is the only application modifying data les. A second instance of that application would then attempt to lock that same le, but the attempt would inevitably fail. Put simply, multiple instances of that application cannot coexist unless they can be isolated from each other.

Even if multiple workloads can coexist, other obstacles to consolidation may be present. Corporate security or regulatory rules might dictate that one group of users must not be able to know anything about programs being run by a different group of users. Either a software barrier is needed to prevent undesired observation and interaction, or those two user groups must be restricted to the use of different systems.

The different user groups might also have application requirements for different OS patch levels, or operate with different system availability and maintenance windows. In general, however, UNIX-like operating systems are good platforms for consolidation because they provide user separation and resource management capabilities and scale well on large platforms. Some other operating systems particularly those that were originally designed to be single-user systems cannot be used as a base for consolidated workloads as easily.

Their architecture can make coexistence of similar workloads impossible and coexistence of different workloads dif cult. Modifying a single-user OS so that it can run multiple workloads concurrently can be much more dif cult than designing this capability into the system at the beginning. The use of these platforms as single-application servers led to the industry mindset of one application per server, even on systems that can effectively run multiple applications simultaneously.

Another solution is needed: the ability or apparent ability to run multiple copies of the operating system concurrently with one workload in each OS, as shown in Figure 1.3. To the hardware, this arrangement does not differ.

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