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Date: Tue, 25 May 2010 08:54:27 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [RFC PATCH 1/1] ceph/rbd block driver for qemu-kvm
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To: Avi Kivity <avi@redhat.com>
Cc: kvm@vger.kernel.org, qemu-devel@nongnu.org, Blue Swirl <blauwirbel@gmail.com>, ceph-devel@vger.kernel.org, Christian Brunner <chb@muc.de>, MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>

On 05/25/2010 08:36 AM, Avi Kivity wrote:
>
> We'd need a kernel-level generic snapshot API for this eventually.
>
>> or (2) implement BUSE to complement FUSE and CUSE to enable proper 
>> userspace block devices.
>
> Likely slow due do lots of copying.  Also needs a snapshot API.

The kernel could use splice.

> (ABUSE was proposed a while ago by Zach).
>
>> If you want to use a block device within qemu, you almost certainly 
>> want to be able to manipulate it on the host using standard tools 
>> (like mount and parted) so it stands to reason that addressing this 
>> in the kernel makes more sense.
>
> qemu-nbd also allows this.
>
> This reasoning also applies to qcow2, btw.

I know.

Regards,

Anthony Liguori