I have been running VMmark on a wide variety of systems in preparation for the benchmark's imminent release. During this exercise, I was able to measure the performance difference between Intel's dual-core (Woodcrest) and quad-core (Clovertown) processors using otherwise identical HP Proliant DL380G5 systems. One system contained two dual-core Intel Xeon 5150 processors (four cores total) running at 2.66 GHz. The other system contained two quad-core Intel Xeon 5355 processors (eight cores total) running at 2.66 GHz. Each system contained 32GB of memory and was connected to the same VM library hosted on an EMC CX-300 storage array. Both systems were running ESX Server 3.0.1.
The figure below shows the benchmark scores as the number of tiles was increased until CPU saturation was reached for each system. The dual-core system became fully saturated when running three tiles whereas the quad-core system became saturated at five tiles.
The systems achieved nearly identical benchmark scores for one and two tiles. This behavior was expected since neither system had exhausted its CPU resources. At three tiles, the dual core system was fully utilized, which limited the score, while the quad core systems continued to scale well due to the additional available CPU resources. The quad-core system delivered a 28% higher score with three tiles. The quad-core system became saturated at five tiles and ultimately achieved a score 70% higher than the dual-core system while supporting 67% more VMs.
Many people have asked how much additional performance quad-core processors can provide over their dual-core cousins. These results should help to answer that question while demonstrating the value of having a representative benchmark for mixed virtualization workloads.