Is there really a performance difference between hypervisors from VMware, Microsoft and Citrix? We put them under a microscope and stress-tested them for days to find out the answer.

There was no overall winner here; no way to say, "This is the best hypervisor for every situation." But some general conclusions can be drawn. For CPU- and memory-intensive applications, XenServer and Hyper-V are attractive and have proven their mettle. For a large number of light to moderate workloads-or if you decide that memory over commit, for example, is important-ESX may be the answer. What is entirely clear, however, is that all three hypervisors are legitimate virtualization platforms, and that no single company has a monopoly on virtualization any longer.

Hyper-V cleaned VMware’s clock. The most expensive hypervisor is also the slowest.

We're pleased to see Hyper-V won 4 of the 11 tests (the others going to XenServer by a less than a horse length). For example, test 2 focused on a large number of heavy workload systems: 1 database server running one midsize database and 12 VMs with a heavy workload of CPU, memory and disk operations. Key takeaways from this test:

·            Hyper-V completed SQLjob 52% faster than ESX.

·            Hyper-V is 2.3 times faster than VMware ESX in CPU for Virtualization Review's hypervisor test operations.

·            Hyper-V is 3 times faster than VMware ESX in test for average RAM operations.