[Gluster-devel] Default quorum for 2 way replication

[Ravishankar N]

On 03/04/2016 05:26 PM, Pranith Kumar Karampuri wrote:
> hi,
>      So far default quorum for 2-way replication is 'none' (i.e. 
> files/directories may go into split-brain) and for 3-way replication 
> and arbiter based replication it is 'auto' (files/directories won't go 
> into split-brain). There are requests to make default as 'auto' for 
> 2-way replication as well. The line of reasoning is that people value 
> data integrity (files not going into split-brain) more than HA 
> (operation of mount even when bricks go down). And admins should 
> explicitly change it to 'none' when they are fine with split-brains in 
> 2-way replication. We were wondering if you have any inputs about what 
> is a sane default for 2-way replication.
>
> I like the default to be 'none'. Reason: If we have 'auto' as quorum 
> for 2-way replication and first brick dies, there is no HA.


+1.  Quorum does not make sense when there are only 2 parties. There is 
no majority voting. Arbiter volumes are a better option.
If someone wants some background, please see 'Client quorum' and 
'Replica 2 and Replica 3 volumes' section of 
http://gluster.readthedocs.org/en/latest/Administrator%20Guide/arbiter-volumes-and-quorum/ 


-Ravi
> If users are fine with it, it is better to use plain distribute volume 
> rather than replication with quorum as 'auto'. What are your thoughts 
> on the matter? Please guide us in the right direction.
>
> Pranith