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Date: Mon, 20 Aug 2012 12:23:51 +0100
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From: Stefan Hajnoczi <stefanha@gmail.com>
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Subject: Re: [Qemu-devel] [RFC V3 0/9] Quorum disk image corruption
	resiliency
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To: =?ISO-8859-1?Q?Beno=EEt_Canet?= <benoit.canet@irqsave.net>
Cc: kwolf@redhat.com, =?ISO-8859-1?Q?Beno=EEt_Canet?= <benoit.canet@gmail.com>, stefanha@linux.vnet.ibm.com, qemu-devel@nongnu.org, blauwirbel@gmail.com, anthony@codemonkey.ws, pbonzini@redhat.com, eblake@redhat.com, afaerber@suse.de

On Mon, Aug 20, 2012 at 11:12 AM, Beno=EEt Canet <benoit.canet@irqsave.net>=
 wrote:
> Le Tuesday 14 Aug 2012 =E0 16:14:02 (+0200), Beno=EEt Canet a =E9crit :
>> This patchset create a block driver implementing a quorum using m qemu d=
isk
>> images. Writes are mirrored on the m files.
>> For the reading part the m files are read at the same time and a vote is
>> done to determine if a qiov version is present n or more times. It then =
return
>> this majority version to the upper layers.
>> When i < n versions of the data are returned by the lower layer the
>> quorum is broken and the read return -EIO.
>>
>> The goal of this patchset is to be turned in a QEMU block filter living =
just
>> above raw-*.c and below qcow2/qed when the required infrastructure will =
be done.
>>
>> Main use of this feature will be people using NFS appliances which can b=
e
>> subjected to bitflip errors.
>>
>> This patchset can be used to replace blkverify and the out of tree blkmi=
rror.
>>
>> usage: -drive file=3Dquorum:n/m:image_1.raw:...:image_m.raw,if=3Dvirtio,=
cache=3Dnone
>
> stefanha: I am wondering what would be needed to do in order to have COR =
and streaming working
> with quorum.c ?

.bdrv_is_allocated()/.bdrv_co_is_allocated() needs to be supported by
block/quorum.c.  Have you tried it and found a problem?

Stefan