Re: [Xen-users] Xen, Heartbeat2 and live migration

[Yann Cezard <yann.cezard@xxxxxxxxxxx>]

Thorolf Godawa a écrit :
> Hi,
>
> > it seems that Suse 10 SP1 allows to migrate Xen VMs between Heartbeat
> > nodes using live migration, where other distros just stop them on a
> > node and start them on another node.
> I don't see any sense to use live migration to get up and running a 
> system that fails on an other node!
> If heartbeat does not response anymore I assume that either the dom0 
> with all domUs crashed, so a migration of any domU is not possible at 
> all, or the specific domU is dead and you will get a dead domU on the 
> new system after migration too (I don't know if you can migrate a dead 
> system)!
> So if the "source" system does not answer anymore, the only way to get 
> it up and running is to start it again on the same or on a different 
> node.
> Live migration is only good for load balancing and planned maintanance 
> issues, not for high availability!
I totally agree with that. It's OK for HA, but what i want is to be able to
planned maintenance on dom0, and so migrating domU on another node.
If I do that with "xm migrate --live ..." heartbeat will see that the 
resource (the domU)
has moved, and it will stop it on the new node, and start it again on 
the first one.
That is definitly not what I want (or perhaps i am missing something ?).

Heartbeat2 allows to migrate resource (Xen domU in our case) from one 
node to another.
But how it works is : it stops the domU on nodeX (one of our dom0 in the 
HB2 cluster),
and starts on nodeY.
A simple modification of the Xen script to use xen live migration in 
this case seems
not to be sufficient, as there is no way to know the destination node in 
it (or we could
hard code the destination in the script, but that is a dirt hack, I 
don't want that).
I think that is where Novell/Suse has done modifications in HB2 code in 
order to
allow that (a way to know the destination node when migrating resource), 
and that's
what I would like to achieve, but without using Novell/Suse.

But perhaps I should better ask on linux-ha mailing list. I just wanted 
to know
if someone here has already done such a thing, or using Suse 10 SP1.

Cheers,

--
Yann Cezard



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