[Gllug] Bits of virtualisation

Paul Hewlett phewlett76 at gmail.com
Thu Dec 29 18:01:52 UTC 2011

On 29 Dec 2011 10:14, "James Courtier-Dutton" <james.dutton at gmail.com>

> On Dec 29, 2011 8:52 AM, "Richard W.M. Jones" <rich at annexia.org> wrote:
> >
> > 64 bit.
> I agree with 64 bit. Much better for if you want to run virtual machines.
> >
> > Put Fedora 16 on the host.  Red Hat has the largest team working on
> > server virtualization and KVM.
> >
I have used virtualbox for the last 3  yrs or so and like it a lot. At one
> point I was using gentoo 64 bit kde as host with a win7 64 bit guest
> running citrix client without any real problems (yes there were 4
> toolbars). I have never used 32 bit except for a WXP guest on my laptop.
However there are 2 problems with virtualbox you should know about .

> Older versions of Virtualbox were a performance hog - even with an idle
> guest OS virtualbox would consume nearly 100% of one CPU - for this reason
> l usually confined guest OS to a single core. There is also.a workaround
> for this - define a dummy guest with nothing in it and start it  - it will
> sit there with an error msg 'system disk not found' and the CPU usage of
> the other guest OS will magically drop to 50%. Latest versions do not
> suffer this problem quite as badly although on starting the guest OS CPU
> usage on my laptop peaks at 110% (dual core host) only to settle at a
> constant 15% once boot of the guest OS (WXP) is complete (host is Ubuntu
> 11.10)
   See  https://www.virtualbox.org/ticket/894 if you are interested.

> The 2nd problem is that virtualbox does not honour the fsync()/sync()
> calls - this results in some I/o benchmarks running faster in a virtualbox
> guest than on native hardware. This never caused a problem for me but has
> been reported on the forums.

> I have recently got Win7 running as a guest OS in KVM using the virtio and
> spice drivers on a Ubuntu 11.10 host. I much prefer this to Virtualbox - I
> use virt-manager gui mostly - this is quite buggy and one has to revert to
> the virsh command to fix things. The Win7  guest reports performance
> metrics 10-20% *better* than Win7 running natively on my sonś laptop.
> However despite my best efforts I could not get the graphics performance
> above 1.0 and could not run Aero as a result. Native graphics for KVM is a
> work in progress. I had to disable the spice drivers as they caused the
> Win7 guest to crash after about an hour

   So I would recommend Virtualbox if the guest OS is a desktop , KVM for
all other cases.

   Lastly I would recommend that you install the kernel with virtio enabled
in your guest images and to use bridged networking (unfortunately this
means disabling NetworkManager). Virtio make a significant difference to
I/O speeds.


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