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Date: Mon, 13 Oct 2014 08:06:29 +0200 (CEST)
From: Alexandre DERUMIER <aderumier@odiso.com>
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Subject: Re: [Qemu-devel] qemu drive-mirror to rbd storage : no sparse rbd
	image
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Ceph Devel <ceph-devel@vger.kernel.org>, qemu-devel <qemu-devel@nongnu.org>

>>Lack of bdrv_co_write_zeroes is why detect-zeroes does not work. 
>>
>>Lack of bdrv_get_block_status is why sparse->sparse does not work 
>>without detect-zeroes.

Ok, thanks Paolo !

Both are missing in rbd block driver. @ceph-devel . Could it be possible to=
 implement them ?



Also, about drive-mirror, I had tried with detect-zeroes with simple qcow2 =
file, 
and It don't seem to help.
I'm not sure that detect-zeroes is implement in drive-mirror.

also, the target mirrored volume don't seem to have the detect-zeroes optio=
n


# info block
drive-virtio1: /source.qcow2 (qcow2)
    Detect zeroes:    on

#du -sh source.qcow2 : 2M

drive-mirror  source.qcow2 -> target.qcow2

# info block
drive-virtio1: /target.qcow2 (qcow2)

#du -sh target.qcow2 : 11G




----- Mail original ----- 

De: "Paolo Bonzini" <pbonzini@redhat.com> 
=C3=80: "Alexandre DERUMIER" <aderumier@odiso.com>, "qemu-devel" <qemu-deve=
l@nongnu.org> 
Cc: "Ceph Devel" <ceph-devel@vger.kernel.org> 
Envoy=C3=A9: Dimanche 12 Octobre 2014 15:02:12 
Objet: Re: qemu drive-mirror to rbd storage : no sparse rbd image 

Il 08/10/2014 13:15, Alexandre DERUMIER ha scritto: 
> Hi, 
> 
> I'm currently planning to migrate our storage to ceph/rbd through qemu dr=
ive-mirror 
> 
> and It seem that drive-mirror with rbd block driver, don't create a spars=
e image. (all zeros are copied to the target rbd). 
> 
> Also note, that it's working fine with "qemu-img convert" , the rbd volum=
e is sparse after conversion. 
> 
> 
> Could it be related to the "bdrv_co_write_zeroes" missing features in blo=
ck/rbd.c ? 
> 
> (It's available in other block drivers (scsi,gluster,raw-aio) , and I don=
't have this problem with theses block drivers). 

Lack of bdrv_co_write_zeroes is why detect-zeroes does not work. 

Lack of bdrv_get_block_status is why sparse->sparse does not work 
without detect-zeroes. 

Paolo