CPU to use for VM (kvm64 vs host type)?

[alexc]

As I create new VM for web site I'm in doubt if I should use kvm64 vs host type of CPU for VM.

Choose host should looks like can give me more real cpu power (but I limited by real physical cores number), while kvm64 can be set to as high as 128, and (as I can imagine) will share the same processing power but divide in into smaller pieces.

As my VM will serve web load then more smaller CPU cores appears to be more useful (like to serve more requests per seconds in parallel), but I'm in doubt.

P.S. The load is general PHP site with MySQL backend, nginx and apache behind it (no way to change this), and https enabled (so h/w acceleration by CPU is useful).

 

[udo]

Hi,
cpu type host make sense only if your processes use cpu-flags which are not in kvm64 - afaik like openvpn can use aes.

To use more cores with kvm64 than your system have (incl. HT) are an bad idea - your VM will be super slow!

If you have an cluster live-mirgation with cpu-host will work only with identical CPUs! (and perhaps identical bios-settings)

Udo