[CentOS] Virtualization platform choice

Thu Mar 31 17:30:34 UTC 2011
Kenni Lund <kenni at kelu.dk>

2011/3/31 David Sommerseth <dazo at users.sourceforge.net>:
> On 29/03/11 21:13, Kenni Lund wrote:
>> The main problem is Windows guests, which easily chokes on hardware
>> changes (forced reactivation of Windows or unbootable with BSOD). Each
>> qemu-kvm version will behave differently, so moving from one major
>> qemu-kvm version to another (0.1x -> 0.1y), will most likely change
>> the virtual hardware seen by the guest, unless you have libvirt etc.
>> configured to keep track of the guest hardware.
>
> Do you know how to set up this?  Or where to look for more details about
> this?  I do have one Windows guest, and I can't break this one.

AFAIR, the BSOD I've seen while moving Windows 2003 Server guests to
new hosts (Fedora 7->8->9->10->11->CentOS5), was caused by old VirtIO
guest block drivers. If you've installed recent VirtIO drivers in the
guest (like virtio-win from Fedora) and are using a recent
kernel/qemu-kvm on the host, then I don't think you'll have any BSOD
or breakage of the guest. You'll need to reactivate once, but that
should be it.

If it was me who were going to move from to CentOS/SL 6 from a non-RH
distribution with a different libvirt/qemu-kvm version, I would not
use the old configuration file directly. Instead I would create a
similar guest from scratch with virt-manager/virt-install, shut down
the guest before installing anything, overwrite the new (empty) image
with your old backup image and then compare the old XML configuration
with the new one and manually move over some specific configurations,
if needed. On first boot, you'll probably have to reactivate Windows,
but at least now you know that the libvirt XML-configuration for the
guest should be compatible with CentOS/SL 6+, and hence have stable
guest hardware in future host upgrades.

You can read some more about it here:
http://fedoraproject.org/wiki/Features/KVM_Stable_PCI_Addresses
http://fedoraproject.org/wiki/Features/KVM_Stable_Guest_ABI

Best regards
Kenni