Xen users - May 2008 - virtualbox vs. xen - ease of domU installation

Folks,

I''ve just started playing with Virtualbox - and boy do they make 
installing virtual machines easy.  Download an .iso of a netinstall CD, 
point Virtualbox at it, and you have a window that behaves just like a 
normal install.  Worked like a charm with both Debian Sarge and Etch 
images - doesn''t seem to require any special bits in the guest O/Ss. 

I did all my playing so far with Virtualbox running under OpenSolaris.  
No problem getting Debian to run, but serious problems with the BSD 
varients, so far.

Miles

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On May 15, 2008 11:54 am Miles Fidelman wrote:
> I''ve just started playing with Virtualbox - and boy do they make
> installing virtual machines easy.  Download an .iso of a netinstall CD,
> point Virtualbox at it, and you have a window that behaves just like a
> normal install.  Worked like a charm with both Debian Sarge and Etch
> images - doesn''t seem to require any special bits in the guest
O/Ss.
VirtualBox is based on a modified QEmu.  It emulates a complete computer, 
right down to the BIOS, including a bunch of standard hardware 
components.  As such, you don''t need to modify OSes to run then on the
VB
VM.  VirtualBox doesn''t (AFAIK) use the hardware virtualisation support
in Intel/AMD CPUs, and does a bunch of software tricks to run the VMs.  
Not sure if it uses the KQemu accelerator module or not, or anything 
similar.  As such, running VMs in VirtualBox will be slower than other 
solutions (that uses accelerator modules, hardware virtualisation 
support, etc).

The closest comparable product for VirtualBox would probably be VMWare 
Server or VMWare Workstation (in how they create a total virtual 
computer, with a pretty management GUI).  They work roughly the same 
(doing everything in software).

Xen can also run unmodified guests OSes when installed on systems with 
motherboards/CPUs that support Intel''s VMX or AMD''s SVM
hardware
virtualisation extensions.  Xen uses a modified QEmu to create the 
hardware VM (emulating a bunch of standard hardware), and as such, you 
can run unmodified guest OSes.

KVM can also run unmodified guest OSes, when installed on systems that 
support VMX/SVM.  KVM uses a modified QEmu to provide standard hardware, 
and can run unmodified guests.

(As all but VMWare use a modified QEmu base, it''s fairly easy to move
VMs
between products.  I''ve run Xen HVM images under KVM, and KVM images 
under QEmu.)

And, of course, there''s also QEmu.  :)

-- 
Freddie Cash
fjwcash@gmail.com

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On Thu, May 15, 2008 at 1:09 PM, Freddie Cash <fjwcash@gmail.com> wrote:
> On May 15, 2008 11:54 am Miles Fidelman wrote:
> > I''ve just started playing with Virtualbox - and boy do they
make
> > installing virtual machines easy.  Download an .iso of a netinstall
CD,
> > point Virtualbox at it, and you have a window that behaves just like a
> > normal install.  Worked like a charm with both Debian Sarge and Etch
> > images - doesn''t seem to require any special bits in the
guest O/Ss.
>
> VirtualBox is based on a modified QEmu.  It emulates a complete computer,
> right down to the BIOS, including a bunch of standard hardware
> components.  As such, you don''t need to modify OSes to run then on
the VB
> VM.  VirtualBox doesn''t (AFAIK) use the hardware virtualisation
support
> in Intel/AMD CPUs, and does a bunch of software tricks to run the VMs.
> Not sure if it uses the KQemu accelerator module or not, or anything
> similar.  As such, running VMs in VirtualBox will be slower than other
> solutions (that uses accelerator modules, hardware virtualisation
> support, etc).
>
>
> --
> Freddie Cash
> fjwcash@gmail.com
>
>From VirtualBoxes website.  Seems they''re using VT some but only
when it''s
faster than their own optimizations (kqemu?).

"Since, however, nearly all operating systems in use today only make use of
ring-0 and ring-3, and since a lot of operations in non-root mode are very
expensive, VirtualBox does not use VT-x exactly as intended by Intel.
Instead, we make partial use of it -- only where it makes sense and where it
helps us to improve performance."

I''ve seen benchmarks (lies and damn lies) that show kqemu keeping up
with
KVM in some circumstances so this makes me wonder too. Is it just smoke and
they haven''t implemented full virtualization or are they really able to
do
some things faster using software tricks?

I''m getting ready to post to all VM mailing lists for recommended tests
and
optimizations. I''d like to do a full battery of tests against VMWare
(if I''m
allowed by law!), Xen, KVM, Kqemu, Parallels and VirtualBox to see where
they fall in terms of performance. Of course I''ll test multiple
configurations like PV drivers, PCI passthrough etc.. so each will run as
fast as it can.

It will be a huge undertaking but I''m curious as I think everyone else
is.
Most benchmarks aren''t objective at all. Maybe I''ll end up
with a dead horse
in my bed for doing this. :-)

Grant


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Quoting Grant McWilliams <grantmasterflash@gmail.com>:
> It will be a huge undertaking but I''m curious as I think everyone
else is.
> Most benchmarks aren''t objective at all. Maybe I''ll end
up with a dead horse
> in my bed for doing this. :-)
>
> Grant
>
Of course if you do succeed you can always tell them, "I aint no band  
leader.".

:)





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On Thursday 15 May 2008, Miles Fidelman wrote:
> Folks,
>
> I''ve just started playing with Virtualbox - and boy do they make
> installing virtual machines easy.  Download an .iso of a netinstall CD,
> point Virtualbox at it, and you have a window that behaves just like a
> normal install.  Worked like a charm with both Debian Sarge and Etch
> images - doesn''t seem to require any special bits in the guest
O/Ss.
>
> I did all my playing so far with Virtualbox running under OpenSolaris.
> No problem getting Debian to run, but serious problems with the BSD
> varients, so far.
Although you still have to be booted into a Xenified kernel, the virt-manager 
app developed primarily by RedHat and shipped in Fedora, RHEL and CentOS 
makes installing Xen guests (all HVM guests, and Redhat-like PV guests) 
similarly friendly.  They were also working on support for Suse PV guests, 
although I don''t know if that came to anything.

Setting up Xen does lack some of the simplicity of being able to install 
something that acts more like a "normal application", though.

Cheers,
Mark

-- 
Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/)

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Mark Williamson wrote:
> On Thursday 15 May 2008, Miles Fidelman wrote:
>   
>> Folks,
>>
>> I''ve just started playing with Virtualbox - and boy do they
make
>> installing virtual machines easy.  Download an .iso of a netinstall CD,
>> point Virtualbox at it, and you have a window that behaves just like a
>> normal install.  Worked like a charm with both Debian Sarge and Etch
>> images - doesn''t seem to require any special bits in the guest
O/Ss.
>>
>> I did all my playing so far with Virtualbox running under OpenSolaris.
>> No problem getting Debian to run, but serious problems with the BSD
>> varients, so far.
>>     
>
> Although you still have to be booted into a Xenified kernel, the
virt-manager
> app developed primarily by RedHat and shipped in Fedora, RHEL and CentOS 
> makes installing Xen guests (all HVM guests, and Redhat-like PV guests) 
> similarly friendly.  They were also working on support for Suse PV guests, 
> although I don''t know if that came to anything.
>
> Setting up Xen does lack some of the simplicity of being able to install 
> something that acts more like a "normal application", though.
>
> Cheers,
> Mark
>
>   
It''s not that good. At last look, it has *no* support for  configuring 
floppy or CD access at install time, no support for multiple virtual or 
physical disks, and no support for using using a Dom0 installed kernel 
in a DomU, as has been supported in Xen since its creation. It needs 
quite a lot of work, and the version in RHEL always lags significantly 
behind that of Fedora. Virt-manager is little better, and does not allow 
modification of a guest domain without shutting it down, which Xen 
itself *DOES* allow with the xm command.

I hope many of these issues have been addressed in FC9, but these sorts 
of issues are why I''m hoping for someone good with Perl to do a decent 
Webmin utility.

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>
>
>> Although you still have to be booted into a Xenified kernel, the
>> virt-manager app developed primarily by RedHat and shipped in Fedora,
RHEL
>> and CentOS makes installing Xen guests (all HVM guests, and Redhat-like
PV
>> guests) similarly friendly.  They were also working on support for Suse
PV
>> guests, although I don''t know if that came to anything.
>>
>> Setting up Xen does lack some of the simplicity of being able to
install
>> something that acts more like a "normal application", though.
>>
>> Cheers,
>> Mark
>>
>>
>>
> It''s not that good. At last look, it has *no* support for 
configuring
> floppy or CD access at install time, no support for multiple virtual or
> physical disks, and no support for using using a Dom0 installed kernel in a
> DomU, as has been supported in Xen since its creation. It needs quite a lot
> of work, and the version in RHEL always lags significantly behind that of
> Fedora. Virt-manager is little better, and does not allow modification of a
> guest domain without shutting it down, which Xen itself *DOES* allow with
> the xm command.
>
> I hope many of these issues have been addressed in FC9, but these sorts of
> issues are why I''m hoping for someone good with Perl to do a
decent Webmin
> utility.
>
> I agree, virt-manager is just barely good enough to use as an interface to
start and stop your domains. I never use it to actually create anything. The
interface that SUSE has is better.

Considering you can do just about anything with the xm command a shell
script with a select menu would do a better job! Well, outside of monitoring
your domains. I actually made a wizard that installed CentOS from premade
kickstart file and web access because I needed to test many different
configurations without me having to install. It was just a couple hundred
line bash script but worked fairly well. I think virt-manager will get
better in the future but I wouldn''t look to Fedora 9 for it because it
can''t
even act as a Dom0 so there''s probably not much use in having an
updated
virt-manager in it.

Grant


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