Subject: Re: [vserver] Pros and Cons of 32/64bit guests on 64bit host
From: Nicolas Cadou <ncadou@cobi.net>
Date: Fri, 22 Aug 2008 08:25:10 -0400
Fri, 22 Aug 2008 08:25:10 -0400
Le August 21, 2008, Stephen Liu a écrit :
> > So you kind of allocate XYZ MB to each virtual machine
> > and
> > you roughly have to live with that commitment
>
>  Please explain in more detail.  On installing the software of virtual
>  machine they don't request alloting XYZ MB RAM.

Since it is a virtual *machine*, you must define its characteristics, like how 
much RAM, how many CPUs, etc...

With KVM you can overcommit, as with others I believe, ie for you 8GB machine 
you can have 4 VMs with 4GB each; physical RAM will get used according to 
each VM's usage.

> > Since the former are kind of complete machine emulations I would
> > assume
> > it's no problem to run vserver under a kvm/vmware image. 
>
>  If I understand your advice correct I can install vserver on the guest
>  running on KVM/VMware image?  A virtual machine on another virtual
>  machine?

Yes, that's the way it is running here. And by the way, I have not measured 
how much overhead the KVM layer actually incurs, but I was simply blown away 
by the performance, compared to VMware Server which I have also used in the 
past. Running speed is pretty near native now.

I would have preferred to run the vservers directly on the host, but there is 
no official Linux-VServer enabled kernel in Ubuntu Hardy, and I don't need 
the maintenance overhead of having to recompile a kernel every now and then, 
so KVM it is for now.

-- 

Nicolas Cadou

Cobi Informatique Inc.
Tel: (450) 266-2420 (305)
Fax: (450) 266-2415


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