File compression / decompression test
Last but not least, I run some file compression and decompression benchmarks. To this purpose, I used the integrated 7-Zip benchmark and another little benchmark that is really a .bat script with the sole purpose of compress and decompress a small zip file (about 6 MB) containing thousands of smaller icon files.
First, let see the 7-Zip results:
Apart Xen, which is slower, VMware, VirtualBox and KVM are quite paired each other. Please consider that the 7-Zip benchmark run entirely in RAM and do not use the disk storage.
What about a more real world, commonly faced situation as compressing and decompressing a .zip file?
This time the primary disk is heavily loaded by the decompress operations. Quite surprisingly, KVM (with its apparently slow disk access time) is very fast to both compressing and decompressing. VirtualBox is also very fast at compressing but not so great at decompressing, while VMware and Xen behave in the exactly opposite manner and are overall the slowest machine.
What can be at play here? It is difficult to give us a very precise interpretation but it seems to me that in the compression test, which is more CPU intensive, KVM and VirtualBox both have a quite strong advantage. In the decompression test, which is generally disk bound, we see that KVM lost the crown probably as a result of its no-so-quick disk subsystem, while Xen and VMware are slightly better. The bad VirtualBox performance surprise me, as in theoretical disk tests it show excellent results.
UPDATE: a recent article comparing KVM vs VirtualBox can be found here: http://www.ilsistemista.net/index.php/virtualization/12-kvm-vs-virtualbox-40-on-rhel-6.html