Host system consolidation results
The final target of a virtualizer is to consolidate as many guests as possible in a single host system. This capability, called consolidation rate, is a key parameter in hypervisor choice: the more it can run guests virtual machine without causing to much overhead, the better is. So, how KVM and Virtualbox fare in this discipline?
As you can see, it seems that Virtualbox has a slightly lower overhead with four and eight guests, but the results with twelve guests are very close. KVM seems to cause a slightly higher I/O load also. However, keep in mind that this is only half of the truth: to depict an accurate representation, we had to consider guests performance also. The reason is clear: if a guest run slower, it will also consume lower CPU time on the host system. In the following pages we well consider guests speed also but, for the moment, lets concentrate on host load.
Consolidation rate is often limited not by CPU speed, but by main memory availability. Who is the most parsimonious between the two contenders?
Well, it seems that while the 4 guests results are very similar, with 8 and 12 guests Virtualbox use more memory than KVM. This is a quite important win for KVM as, by judging from the above trend, it seems that Virtualbox's disadvantage will grow with more guests.