I am planning to develop an automated test solution with multiple windows machines and multiple ubuntu machines that perform related/interdependent tasks. To start the project, I'd like to have one or two windows machines (virtual) and a few ubuntu machines (virtual) running on a single desktop. It seems likely that I will be pushing a single desktop to the limit here so I am trying to guess if I will have better luck if my host OS is ubuntu or if it is Windows 7. I would be able to use the host OS as one of the machines in my environment. The desktop is some sort of above average Dell, but nothing really impressive.
Does anyone have any insight here? I've worked mostly with VMWare in the past and my host was windows along with my VMs.
Note: VirtualBox is a type-2 hypervisor (it runs on the host OS, not on the hardware like a type-1 hypervisor) and tends to offer weaker performance than, for example, Hyper-V, ESX or XEN (type-1 hypervisors).
Therefore, if performance is a considerable concern, you may squeeze more juice out of Win8 or Windows Server 2012 box running, for example, Hyper-V. Further reading on this here and here (YMMV).
How your environment will run when hosted by a Windows vs. a Linux box is, frankly impossible to tell. I suggest you build your VM's and try dual-booting your machine in Windows and Linux and measuring your scenario. Be sure to have enough RAM in the host to allocate enough working RAM to each VM and enough IO throughput that your host doesn't end up dragging the perf of all VM's down if one VM saturates the machine's IO.
One last note of caution though: Don't completely trust fine-grained perf results measured on VM's - even the best hypervisors cannot truly replicate the perf' characteristics of code running on bare-metal. Treat your measurements as a guideline only.
Measure, then measure again. Measure again just to be sure ... and THEN tweak your config and re-measure, measure, measure ;)