In this Developer Summit article: http://proceedings.esri.com/library/userconf/devsummit10/tech/tech_12.html Page 50 and 51 speak to performance degradation using various configured VMs compared to a physical 1P_4C_16R server. Is this suggesting that a 4V_1C_2R, with 4 SOCs, performs ~11% worse than a "single machine (SOC, SOM, WS) ArcGIS Server deployment" on a 1P_4C_16R?
Yes, for that particular configuration and service the VM's throughput was 11% lower then the physical server. The key item is to test your particular services and configuration before production deployment as the amount of degradation can vary significantly. Additional information may be found in the VMWare/Esri virtualization whitepaper.
