Re: [Qemu-devel] [PATCH v5 0/3] Quorum maintaince operations

[Benoît Canet]

The Saturday 31 May 2014 à 20:47:47 (+0200), Max Reitz wrote :
> On 31.05.2014 20:45, Benoît Canet wrote:
> >The Friday 30 May 2014 à 19:53:12 (+0200), Max Reitz wrote :
> >>On 30.05.2014 13:18, Benoît Canet wrote:
> >>>These are the last bits required to make quorum usable in production.
> >>>
> >>>v5:     rebase on latest Stefan's block branch [Kevin]
> >>>
> >>>v4:
> >>>         update patchset to stefan's block branch
> >>>                 drop Max reviewed by because the series changes
> >>>
> >>>Benoît Canet (3):
> >>>   quorum: Add the rewrite-corrupted parameter to quorum.
> >>>   block: Add drive-mirror-replace command
> >>>   qemu-iotests: Add 096 new test for drive-mirror-replace.
> >>Independently of this series, while looking at patch 1 again
> >>(although I had reviewed it before already), I noticed that
> >>quorum_get_winner() does not select the definite winner, but only a
> >>winner. So if you have a quorum instance with four children and a
> >>threshold of two, it may happen that there are basically two winners
> >>which both fulfill the threshold condition. In this case,
> >>quorum_get_winner() will just return the first winner. However, I
> >>think it should then return that there is no winner (i.e., NULL).
> >>
> >>On the other hand, the user should be aware that it may be a bad
> >>idea to choose a threshold which does not exceed half of the
> >>children count; thus, I'm just asking what you think about this. :-)
> >I think Quorum n/(2 *n) is a bad idea. (n + 1) / (2 *n) is a least required.
> >
> >I wonder where we could put some documentation about this for the user.
> 
> Well, quorum_valid_threshold() exists and could check this… Maybe it
> could at least emit a warning?
> 
> Max

Thanks,

Good idea I will write a patch doing this.

Best regards

Benoît
> 
> >Best regards
> >
> >Benoît
> >
> >>Max
> >>
> 
>