[geeks] the virtualization project

[Shannon]

On 10-Sep-2011 15:19, Bill Bradford wrote:
> On Fri, Sep 09, 2011 at 12:51:16PM -0400, Shannon wrote:
>> Are you running them using hardware virtualization? I didn't see another way
>> under KVM, and that's one thing I wanted to avoid if I were going to run
>> several OS.
> 
> Yes.  
> 
>> I am looking at KVM but there were two issues that came up. One is its that it
>> seems to require HVM (hardware virtualizatin) even if you have paravirtual
>> drivers (virtio). I tried it on my AMD Opteron system and it just refused to
>> work, and from what I read it is the lack of HVM support on that CPU.
> 
> Why are you against hardware virtualization?  You just want it to work on
> what you've got now?

I didn't say I was against it, I use it every day. I said it has some
issues and listed them I thought. Just talking about the pros and cons
of the different systems I am looking at and testing.

HVM is basically a hack on AMD and Intel CPUs to create a restricted
ring zero which traps hardware accesses to a "ring -1" hypervisor. Its
not very pretty and tends to be slower and heavier calls than the
hypercalls used by guest OS in something like Xen.

So its advantage is it will run almost any OS even if it can't be
modified, but you pay a price in heavier emulation overhead.

Xen is generally going to be faster, unless the guest OS drivers are poor.

Linux KVM is sort of a hybrid, but unfortunately will not run on non HVM
CPUs, and I as I said for performance I prefer to avoid HVM unless I
have no other choice.

Its probably the most flexible solution right now: Linux has the most
mature Xen support and is only one of two OS that can do KVM. Someone
ported KVM to Solaris but I don't know how well that works.