Re: [Qemu-devel] [RFC V5 09/11] quorum: Add quorum_getlength().

[Benoît Canet]

Le Monday 27 Aug 2012 à 12:03:48 (-0600), Eric Blake a écrit :
> On 08/27/2012 01:30 AM, Benoît Canet wrote:
> > Signed-off-by: Benoit Canet <address@hidden>
> > ---
> >  block/quorum.c |   24 ++++++++++++++++++++++++
> >  1 file changed, 24 insertions(+)
> 
> Say I'm using a 2/3 quorum.  What happens if:
> 
> image A and B agree on initial content, but not length
> image B and C agree on length, but not content
> 
> Does disagreeing with quorum consensus invalidate that member of the
> quorum from influencing further decisions?  If there is a length
> discrepancy, should we declare the quorum failed rather than relying on
> a mere majority vote?  Or, if there is a length discrepancy, does
> reading the contents beyond the end of the shorter files consider the
> contents to be okay if the longer files have only NUL bytes in the extra
> length?  I'm worried that you haven't fully thought through all the
> scenarios here.

True,
Maybe I shoud just check that every quorum file have the same length
and return 0 on error. This way the quorum in disabled in case of length
discrepancy.

> 
> -- 
> Eric Blake   address@hidden    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
>