Back in June, I wrote about some scale-up experiments that we conducted with SAP software on vSphere 4. That work focused on a single VM, so we decided to follow it up with a study of multiple VMs on a single server. Collaborating with IBM, we performed experiments to study the scale-out behavior of SAP software: using vSphere 4 to run multiple VMs on a 24-core IBM x3850 M2. We presented this joint work at VMworld 2009 (EA 1640), and have recently written a whitepaper that contains the results: ftp://ftp.software.ibm.com/eserver/benchmarks/wp_x3850M2_VMware_SAP_Scaling_112009.pdf
This new whitepaper highlights the fairness of scheduling in vSphere and the hardware features of the x3850 M2 that allowed us to run 12 concurrent 2vCPU VMs with excellent performance. In addition, we showed that a variety of choices of vCPU count and VM count are possible with very little impact on performance (see figure).