I do not think a quorum feature does a fair job in a 2 way replication. The minimum criteria to use quorum is 3 and it does not make any sense to me to turn it on by default for 2 way replication especially when HA is not achieved if the 1st brick the pair goes down.
BTW, whats the history behind this limitation? -Atin Sent from one plus one On 04-Mar-2016 6:00 pm, "Pranith Kumar Karampuri" <[email protected]> wrote: > > > On 03/04/2016 05:47 PM, Bipin Kunal wrote: > >> HI Pranith, >> >> Thanks for starting this mail thread. >> >> Looking from a user perspective most important is to get a "good copy" >> of data. I agree that people use replication for HA but having stale >> data with HA will not have any value. >> So I will suggest to make auto quorum as default configuration even >> for 2-way replication. >> >> If user is willing to lose data at the cost of HA, he always have >> option disable it. But default preference should be data and its >> integrity. >> > > That is the point. There is an illusion of choice between Data integrity > and HA. But we are not *really* giving HA, are we? HA will be there only if > second brick in the replica pair goes down. In your typical deployment, we > can't really give any guarantees about what brick will go down when. So I > am not sure if we can consider it as HA. But I would love to hear what > others have to say about this as well. If majority of users say they need > it to be auto, you will definitely see a patch :-). > > Pranith > >> >> Thanks, >> Bipin Kunal >> >> On Fri, Mar 4, 2016 at 5:43 PM, Ravishankar N <[email protected]> >> wrote: >> >>> 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 >>>> >>> >>> >>> > _______________________________________________ > Gluster-devel mailing list > [email protected] > http://www.gluster.org/mailman/listinfo/gluster-devel >
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