[CentOS] Stop the FUD Xen is not deprecated

Pasi Kärkkäinen pasik at iki.fi
Thu Nov 27 10:00:13 UTC 2008

On Tue, Nov 25, 2008 at 06:43:14PM +0000, Ned Slider wrote:
> Brett Serkez wrote:
> >On Tue, Nov 25, 2008 at 10:45 AM, Vandaman <vandaman2002-sk at yahoo.co.uk> 
> >wrote:
> >>Do people have wet underwear for nothing over XEN?
> >>
> >>See http://www.redhat.com/promo/qumranet/
> >>
> >>As far as CentOS is concerned saying Xen is deprecated is
> >>jumping the gun. CentOS ships with Xen and as long as upstream
> >>supports it, CentOS by extension supports it.
> >
> >Thank you for the clarification.
> >
> >What isn't clear from reading the above referenced material is if Xen
> >will be included in future CentOS releases.
> >
> Which is why I originally wrote...
> "*Some* are interpreting this... as an indication that xen will be 
> dropped from RHEL6 as they direct their efforts towards KVM."
> *If* xen is not included in RHEL6 then it will, by definition, be 
> deprecated in favour of KVM irrespective of whether (or not) RH 
> continues to support it throughout the life of RHEL5. Note that xen was 
> dropped (not deprecated, dropped) in Fedora 10, read into that what you 
> will :)

Xen is NOT dropped in Fedora 10. Fedora 10 contains xen-hypervisor,
xen-tools/libs and domU kernel.. and of course all the usual virt-tools. 

Fedora 10 does not include dom0 capable xen kernel. Fedora 9 didn't include
that either. Fedora 8 is the latest Fedora release (at the moment) to include
Xen dom0 support.

Fedora 9 and Fedora 10 both contain Xen domU capable kernels, and they can
be used as Xen guests/domUs. 

The reason why F9/F10 do not include Xen dom0 kernel is the fact that dom0 support 
is not yet included in mainline/vanilla Linux kernels. Fedora didn't want to
forward-port separate non-mainline patches for dom0 support.

This is currently being worked on, and pv_ops dom0 support is currently
planned for inclusion in Linux 2.6.29. 

See: http://wiki.xensource.com/xenwiki/XenParavirtOps
And: http://xenbits.xen.org/paravirt_ops/patches.hg/ (for latest pv_ops dom0 patches)

Fedora will re-add Xen dom0 support into the kernel when it's included upstream.

> So xen isn't technically deprecated yet, but if I were a betting man, I 
> wouldn't be putting all my eggs in a virtualized xen basket.
> Some might choose to call that FUD, and that's their prerogative. In a 
> way they're right as Red Hat's statement on xen does contain elements of 
> uncertainty and doubt as they have not committed to continued ongoing 
> support of xen past the current RHEL5 product lifecycle, and that may 
> make some fearful for it's long term future within the Red Hat landscape.

It's interesting to see what will happen.. At the moment Xensource is
actively working on getting pv_ops based dom0 support into vanilla Linux

The lack of dom0 support in the standard upstream kernel is the only
reason why Fedora 9/10 do not ship with Xen dom0 support.. afaik.

(Efforts needed to continuously forward-port Xenlinux dom0 patches from 2.6.18 to
current 2.6.2x kernels was too big pain to handle.)

-- Pasi

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