SAP Solutions on VMware Best Practices Guide
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© 2011 <strong>VMware</strong>, Inc. All rights reserved.<br />
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<str<strong>on</strong>g>SAP</str<strong>on</strong>g> <str<strong>on</strong>g>Soluti<strong>on</strong>s</str<strong>on</strong>g> <strong>on</strong> <strong>VMware</strong><br />
<strong>Best</strong> <strong>Practices</strong> <strong>Guide</strong><br />
Note that <str<strong>on</strong>g>SAP</str<strong>on</strong>g> has c<strong>on</strong>ducted tests <strong>on</strong> virtual CPU overcommitment (documented in Note 1122388), and<br />
shows the performance degradati<strong>on</strong> inside the virtual machines is linearly reciprocal to the overcommitment.<br />
As the performance degradati<strong>on</strong> is ―graceful,‖ any virtual CPU overcommitments can be<br />
effectively managed by using vMoti<strong>on</strong> to migrate virtual machines to other ESX/ESXi hosts to obtain more<br />
processing power.<br />
Hyperthreading technology (recent versi<strong>on</strong>s of which are called symmetric multithreading, or SMT) allows<br />
a single physical processor core to behave like two logical processors, essentially allowing two<br />
independent threads to run simultaneously. Unlike having twice as many processor cores—which can<br />
roughly double performance—hyper-threading can provide anywhere from a slight to a significant<br />
increase in system performance by keeping the processor pipeline busier. For example, an ESX/ESXi<br />
host system enabled for SMT <strong>on</strong> an 8-core server sees 16 threads that appear as 16 logical processors.<br />
Recent <str<strong>on</strong>g>SAP</str<strong>on</strong>g> benchmarks were c<strong>on</strong>ducted <strong>on</strong> SMT-enabled servers—these are covered in Secti<strong>on</strong> 8.
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