Re: Virtualization preferences

["Jerry Feldman-2" <user=4@nabble.blu.org>]

 On Fri, 25 Jul 2008 22:46:24 -0400 
Christoph Doerbeck <[hidden email]> wrote: 

> The requirement for VTx is only if you plan to use full virt (which has 
> always been the case).  I do not believe there is such a case for para 
> virt.  The only 'requirement' is for PAE, which you won't find (for 
> example) on older pentium mobility processors.  Please correct me if I 
> am wrong on this. 
> 
> Regarding upgrading the host and winding up with broken guests... I know 
> that on Fedora 5 (I think) there was a time when upgrading the host OS's 
> (Dom0) xen kernel could have left you in a bind because it introduced a 
> dependency for PAE support in the guest OS's (DomU). Thus if you didn't 
> upgrade the guests first, you where hosed. 
> 
> Otherwise, I've been pretty successful as far as I can recall with 
> running PV guests and hosts with dissimilar versions (within reason). 
> But I'd expect that if you want to make use of live migration, suspend, 
> resume, etc... I'd probably advise thoughtful planning and upgrade 
> schedules to keep things closer in sync. 
> 
> Last, I don't know if everything Red Hat has done filters down to 
> CentOS ... [but assuming it does] ...  Part of what Red Hat did when 
> integrating Xen into Enterprise Linux, was to insulate the user from the 
> hypervisor implementation.  Meaning, the tooling for managing virtual 
> machines is built on project libVirt ... and essentially ... down the 
> road if Xen is not the "in" technology, then it can be replaced by (or 
> augmented with) kvm, or what ever ... and your tools, scripts, knowledge 
> stays the same.