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Date: Sun, 12 Oct 2014 15:02:12 +0200
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Subject: Re: [Qemu-devel] qemu drive-mirror to rbd storage : no sparse rbd
	image
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To: Alexandre DERUMIER <aderumier@odiso.com>, qemu-devel <qemu-devel@nongnu.org>
Cc: Ceph Devel <ceph-devel@vger.kernel.org>

Il 08/10/2014 13:15, Alexandre DERUMIER ha scritto:
> Hi,
> 
> I'm currently planning to migrate our storage to ceph/rbd through qemu drive-mirror
> 
> and It seem that drive-mirror with rbd block driver, don't create a sparse image. (all zeros are copied to the target rbd).
> 
> Also note, that it's working fine with "qemu-img convert" , the rbd volume is sparse after conversion.
> 
> 
> Could it be related to the "bdrv_co_write_zeroes" missing features in block/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