Re: [Xen-users] migrating between different hardware (xen-3.1.3)

[Stephan Seitz <s.seitz@xxxxxxxxxxxx>]

I don't want to argue against your decision, but you're able to build
your domU kernel with "generic x86" support.

Anyway, we made a few assumptions:
        - heterogene clusters are harder to manage by default
          (even without xen)
        - new x86 hardware supports virtually all features of
          current one.
        - hardware upgrades (10Gbit NICs, Infiniband, ...) are
          likely to be necessary earlier than x86 changes
        - regular updates and kernel patches are always necessary,
          optimization for newer hardware can be done if support
          for older hardware has become obsolete.
        - electricity tends to get expensive

Taking this assumptions, and having in mind that a cluster does not
necessarily need to cover every and all machine, our decision is clear ;)

But to your question. I don't know what kind of automation you're using
for migration, but it's not too hard to get /proc/cpuinfo of a remote
host to check the capabilities before calling xm migrate.
For complex scenarios, some work has always been done outside xen.

Cheers,

Stephan


b52@xxxxxxxxx schrieb:
> I already thought that, but hoped there is a way to tell the domU which
> cpu flags to use. Well this will be the reason my company will not use xen
> for domain management. You will never know what kind of CPUs you will buy
> in future and sure you don't want to buy a complete new cluster because
> you need one box more..
>
> Btw. should the relocation daemon not at least check the CPU flags of the
> remote server before migration?
>
> And there is really no way to pin the domU to a set of CPU flags?
>
> -- Holger
>
> > This has been brought up a few times on the list.  The problem is the cpu
> > features that the guest is using.  When you transfer a domain from the p4
> > to
> > the a64, it supports all the flags (being a generation or two newer) that
> > the p4 does, however in reverse it is not the case.
> >
> > There was some ongoing work to create a filter for domain creation that
> > would allow the 'lowest common denominator'.  However, it seems it's never
> > made into the codetree.  It has been listed on the xen roadmap for a long
> > time now.
> >
> > In short, this doesn't work now, and unless somebody completes the feature
> > filter, it may not work for some time.
> >
> > You should be careful to ensure that all the hosts that you transfer to do
> > in fact support all the cpu flags that the creating host does, otherwise
> > you
> > will run into seemingly random crashes, corruption, or hangs.
> >
> > For the moment, it is only recommendable to do domain transfer between
> > identical (or same generation same lineup) cpus.
> >
> > -----Original Message-----
> > From: xen-users-bounces@xxxxxxxxxxxxxxxxxxx
> > [mailto:xen-users-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of b52@xxxxxxxxx
> > Sent: February 23, 2008 4:13 AM
> > To: Xen-users@xxxxxxxxxxxxxxxxxxx
> > Subject: [Xen-users] migrating between different hardware (xen-3.1.3)
> >
> > Hi,
> >
> > I setup a testbed todo some migration tests for work and got a problem..
> >
> > I used two P4 2.4GHz an AMD64 4200+ (SVM) and an Intel C2D 6320 1.86GHz. I
> > had xen 3.1.3 with 2.6.18 and exactly the same versions on all systems
> > (mirrored AoE) and one 32Bit domU
> >
> > Now if I created this domU on one of the P4s, I was able to migrate it
> > between every host.
> > If I created this domU on the AMD or Intel C2D, it was only possible to
> > migrate between these both. The domU always crashed if I tried to migrate
> > it to the P4s.
> >
> > You can find the xm info of all 4 PCs and one xm log of source(AMD) and
> > one xm log of destination(P4) in close.
> >
> > Any help is appreciated and please CC me
> > Cheers,
> > Holger
> >
> >
> > _______________________________________________
> > Xen-users mailing list
> > Xen-users@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-users
>
>
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> http://lists.xensource.com/xen-users

--
Stephan Seitz
Senior System Administrator

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