The VMware Performance Team just published an interesting ESX Server 3.5 benchmark about Red Hat Enterprise Linux 4 64bit guest running as a web server on top of HP ProLiant DL 385 G1 servers.
To complete the analysis VMware didnt’ use its own benchmarking framework, VMmark, but rather relied on the industry standard SPECweb2005.
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There are different dimensions to performance. For real-world applications the most significant of these are usually overall latency (execution time) and system throughput (maximum operations per second). We are also concerned with the physical resource utilization per request/response.
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The part of the curve marked “Performance plateau” represents the behavior of the system under moderate stress, with CPU utilizations typically well below 50%. Interestingly, we observed lower latency in the virtual environment than in the native environment. This may be because ESX Server intelligently offloads some functionality to the available idle cores, and thus in certain cases users may experience slightly better latency in a virtual environment.
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From this graph we can draw the following conclusions:
- When the CPU resources in the system are not saturated, you may not notice any difference in the application latency between the virtual and physical environments.
- The behavior of the system in both the virtual and physical environments is nearly identical, albeit the knee of the curve in the virtual environment occurs slightly earlier (due to moderately more CPU resources being used by the virtualized system).
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VMware also published a 35-pages whitepaper about the topic, detailing the approach used for system tuning and measurement with SPECweb2005.
Download it here.