Re: [Xen-users] Xen-DRBD Migration question

[Eric Laflamme <elaflamme@xxxxxxxx>]

Hi James,

Yes, this is exactly our point to do migration without allowing two primaries.

We have tested the other way to migrate but none seems to work. Saving the vm 
doesn't stop the vm to be listed in xm list. If I destroy the save vm, then the 
restore fail. So our conclusion is that a save vm can't be restore on another 
host.

Also the save feature takes a lot of time to complete, since our VM have 32 gig 
of ram. So it create a 22 gig save file...

I don't know why migration and even live migration need primaries.. why the 
system can't just put in secondaries for a less than a second to put the other 
host in primary to start the vm?

If you have other ideas.. let me know so I can test it.

-- 
Eric Laflamme [iWeb]
IT Architecture Specialist
Spécialiste de l'Architecture TI
http://www.iWeb.com/




Le 2010-08-10 à 19:40, James Harper a écrit :

>> 
>>> I've heard from a post somewhere that a migration Secondary-Primary
> can be
>> done. Our best way to do this will be to put de VM on pause. Put the
> drbd disk
>> on Secondary. Then migrate the vm to the second host, then put the
> drbd disk
>> on second host to primary and unpause the vm. I've searched on google
> and I
>> can't find anything on this method.
>>> 
>>> Is there a way to do this? Is there another way you are thinking of?
>> 
>> What about a drbd device per vm, both set active/active?  Migration
>> already ensures that only one vm at a time can write to the underlying
>> device through its pause/unpause mechanics.
>> 
> 
> I can't speak for the OP but one of the attractions about
> primary/secondary drbd for me is that you can't accidentally start the
> vm on two nodes at once, ever. It would be nice to have the migration
> handle the volume state transition automatically as I don't think there
> is ever actually a need to have the drbd volume writeable on both nodes
> at once, although a drbd volume isn't even open-able unless it's in the
> primary state.
> 
> James
> 
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