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Date: Tue, 02 Oct 2012 12:09:44 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] Block Migration and xbzrle
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To: Peter Lieven <pl@dlhnet.de>
Cc: "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "kvm@vger.kernel.org" <kvm@vger.kernel.org>

Il 02/10/2012 11:44, Peter Lieven ha scritto:
> 
> Am 02.10.2012 um 11:38 schrieb Paolo Bonzini:
> 
>> Il 16/09/2012 12:39, Peter Lieven ha scritto:
>>>
>>> I remember that this was broken some time ago and currently with
>>> qemu-kvm 1.2.0 I am still not able to use
>>> block migration plus xbzrle. The migration fails if both are used
>>> together. XBZRLE without block migration works.
>>>
>>> Can someone please advise what is the current expected behaviour?
>>
>> Block migration is broken by design.  It will converge really slowly as
>> soon as you have real load in the VMs, and it will hamper the
>> convergence of RAM as well.
>>
>> Hopefully a real alternative will be in 1.3 (based on drive-mirror on
>> the source + an embedded NBD server running on the destination), then in
>> 1.4 we can reimplement the block migration monitor commands using the
>> alternative.
> 
> Hi Paolo, i know that block migration is not that good, but it seems that
> there is a bug in XBZRLE that is independent of block migration.

Understood---but hopefully you can stop using it with 1.3, which would
also work around the bug. :)

Paolo