virtualbox.org

Sometime soon, I'm supposed to get a new iMac to replace my existing 2007-vintage iMac. When that happens, I'll be looking for a new purpose for the old iMac, and one possibility is using it to replace a pair of old decrepit Dell boxes currently running FreeBSD and Windows. One Dell box has 512 MB RAM, and the other has 1 GB. The iMac has 4 GB, and more powerful processor, so I think it should be able to handle the load of both of them via virtualization. (Neither one has a very heavy workload).

Does anybody have any suggestions about which OS to use for the host? I guess my choices would be Lion, Snow Leopard, or Windows 7 via Boot Camp. The machine is currently running Lion, but I wouldn't mind installing a different OS if it would be better or lower overhead. In fact, even if I stay with Lion, I'll probably reinstall it, so installing a new OS isn't a problem. I don't think I'll use the system for anything else other than a host for the 2 VMs, so user interface doesn't really matter. I suppose my main interest would be whether there is a significant difference in reliability or overhead between the different host OS/

After thinking about this a little more, the answer seems obvious. If I just want a Windows system and a FreeBSD system, it seems silly to run them both as guests on a third OS as host. The most efficient config would seem to be Windows running "native" via BootCamp, with a FreeBSD guest. Two systems are more efficient than 3. Right?

That's true, but you have to consider the Windows license (though not much of a problem with retail) and how easy it is to create a backup and restore the system in case it breaks. For that, it would be easier to use the two systems as a VM, as you can just copy the VM folder to any other location or media. When the iMac fails, you can just get a new system, install VB, add the VMs to the manager and start them.

For that, I suggest you get a Linux release instead. E.g. Debian Stable with the VB repo added and the LXDE desktop environment. You can also pick Xfce4 if you want a bit more complete environment, but as you said, it doesn't matter what it runs, as long as you can start a VM (so you could also go with xnomad, openbox, fluxbox, icewm, whatever). Lion will probably use more RAM than Linux with almost nothing installed, so the more RAM you have left, the better it is as you can give more to the VMs.