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

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Subject: Re: [Xen-users] Xen-DRBD Migration question
From: Bart Coninckx <bart.coninckx@xxxxxxxxxx>
Date: Wed, 11 Aug 2010 09:47:50 +0200
Cc: Eric Laflamme <elaflamme@xxxxxxxx>, James Harper <james.harper@xxxxxxxxxxxxxxxx>, John Madden <jmadden@xxxxxxxxxxx>
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On Wednesday 11 August 2010 01:40:07 James Harper wrote:
> > > 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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What we basically do is have a iSCSI target on TOP OF DRBD. It does take two 
more servers, but yuo have a nice HA solution where one servers is passive and 
the other is active. Of course, nothing stops you from having more than one 
DRBD resource runninng on the different nodes connected to different IP 
addresses, sort of to distribute the load. Migration works flowlessly on a 
setup like that.


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