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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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24.5 Virtualization<br />

Virtualization is the logical representation of resources not inhibited by physical<br />

boundaries. The main objective of virtualization is to simplify the IT infrastructure.<br />

It simplifies access to resources <strong>and</strong> the management of those resources. A user<br />

accesses the required service through st<strong>and</strong>ard interfaces supported <strong>and</strong><br />

maintained by the virtualized resource. The st<strong>and</strong>ard interfaces allows<br />

availability issues to be minimized when changes to the IT infrastructure occur.<br />

There many types of virtualization, <strong>and</strong> we describe some in the following<br />

sections.<br />

For additional information, refer to:<br />

► The <strong>IBM</strong> developerWorks® article “Virtualization in a nutshell: A pattern point<br />

of view”<br />

http://www.ibm.com/developerworks/grid/library/gr-virt/<br />

► The <strong>IBM</strong> Redpaper Virtualization <strong>and</strong> the On Dem<strong>and</strong> Business, REDP-9115<br />

http://www.redbooks.ibm.com/redpapers/pdfs/redp9115.pdf<br />

Server virtualization<br />

Many applications cannot be hosted on the same physical server due to resource<br />

conflicts. This creates issues regarding the number of servers deployed as well<br />

as the utilization of the existing resources. This lack of utilization is expensive,<br />

especially considering the cost of wasted storage space, server processing<br />

ability, <strong>and</strong> network utilization. Server virtualization is one way to resolve these<br />

issues.<br />

Server virtualization is used to detach the applications from the physical<br />

configurations <strong>and</strong> limitations. Server virtualization is generally used as an IT<br />

optimization technique <strong>and</strong> has numerous benefits regarding availability <strong>and</strong><br />

scalability.<br />

Server virtualization provides the flexibility to dynamically change the allocation<br />

of system resources for the virtualized environments. The virtual servers can run<br />

on any of the physical machines. This means that the machine resources are<br />

fully shared. This makes it possible to run the physical server at high utilization<br />

levels. In addition, if any of the underlying physical resources need to be<br />

changed, it does not affect the virtualized servers. This enhances the level of<br />

scalability <strong>and</strong> availability associated with each virtual server.<br />

Another aspect of availability to consider is if one of the virtual server instances<br />

fails. In such a case, it does not affect any of the other virtual servers currently<br />

residing on the same physical machine. Each instance of the virtual servers is<br />

912 <strong>TCP</strong>/<strong>IP</strong> <strong>Tutorial</strong> <strong>and</strong> <strong>Technical</strong> <strong>Overview</strong>

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