Re: [Qemu-devel] [RFC V3 0/9] Quorum disk image corruption resiliency

["Benoît Canet" <benoit.canet@irqsave.net>]

Le Monday 20 Aug 2012 à 12:24:33 (+0100), Stefan Hajnoczi a écrit :
> On Mon, Aug 20, 2012 at 12:23 PM, Stefan Hajnoczi <stefanha@gmail.com> wrote:
> > On Mon, Aug 20, 2012 at 11:12 AM, Benoît Canet <benoit.canet@irqsave.net> wrote:
> >> Le Tuesday 14 Aug 2012 à 16:14:02 (+0200), Benoît Canet a écrit :
> >>> This patchset create a block driver implementing a quorum using m qemu disk
> >>> 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 be
> >>> subjected to bitflip errors.
> >>>
> >>> This patchset can be used to replace blkverify and the out of tree blkmirror.
> >>>
> >>> usage: -drive file=quorum:n/m:image_1.raw:...:image_m.raw,if=virtio,cache=none
> >>
> >> 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?
> 
> Just want to confirm you are thinking about image streaming on top of
> quorum?  Or are you thinking about streaming underneath quorum?

I am thinking about streaming with quorum on top of a bunch of backing files.
ie: data landing into the higher level backing file living just under quorum.

Benoît
> 
> Stefan