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Hi, all:

	I have planned to add the support to create qcow2 format file in NFS driver ([1]). From the comment of Eric Harney, I know that cinder-backup service currently assumes the volume is raw-formatted, and enable creating qcow2 in NFS driver will break backups of NFS volumes . 

	After reading the code of backup service, I find we can first mount the qcow2 volume as a NBD device and then pass the NBD device as the "source volume_file" to backup service. Similar method of mounting qcow2 as NBD device has already used in Nova now. I think we can add it to NFS driver for backup, and it can be used for GlusterFS too.

	Any advice? Is there something I have not expected?

[1] https://review.openstack.org/#/c/92011/

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zhangleiqiang (Trump)

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