What Can Virtualization Do For You?
Most high end servers have the capability of partitioning their resources into multiple logical domains, such as HP’s nPars or IBM’s lPars, however, each instance must have an entire processor and the associated memory and I/O subsystems. True virtualization allows fractional amounts of hardware resources to be dedicated to a particular instance, but this capability is restricted to the most expensive systems, such as an IBM’s zSeries or an HP’s Tandem system. Intel is looking to leverage their experience working with virtualization on the Itanium and bring these advances to their entire line of server processors.
Based on several case studies, Intel has concluded that the average Xeon processor could host 2-4 guest servers . This would enable end users to consolidate dozens of 1-2P servers onto several larger systems. In one case, an end user was able to migrate from over 250 2P servers to 10 8P Xeon based machines. This reduces the overall cost of supporting the necessary applications, and can increase the reliability and availability, by hosting virtual servers on more robust platforms and having fewer possible points of failure.
However, virtualization does not come without potential costs. The transitions in and out of the VM state can cause up to a 40% performance penalty, such as in the current IA64 hardware compatibility scheme. The actual performance degradation depends on the application, and the hosting system. Some solutions, such as HP’s Dynamo actually increase the performance of hosted applications; hence, there is no general formula to predict the impact of virtualization. However, end users have implemented virtualization to achieve between 3:1 and 30:1 consolidation ratios .
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