[Gluster-users] Clarification on cluster quorum

[James]

A quick search reveals:

        # Sets the quorum percentage for the trusted storage pool.
        cluster.server-quorum-ratio

        # If set to server, enables the specified volume to
participate in quorum.
        cluster.server-quorum-type

        # If quorum-type is "fixed" only allow writes if this many
bricks or present. Other quorum types will OVERWRITE this value.
        cluster.quorum-count

        # If value is "fixed" only allow writes if quorum-count bricks
are present. If value is "auto" only allow writes if more than half of
bricks, or exactly half including the first, are present.
        cluster.quorum-type

I took these from my previous "notes" (code) in:
https://github.com/purpleidea/puppet-gluster/blob/master/manifests/volume/property/data.pp#L18

You can get newer values or appropriate values for your version by
running something like:

gluster volume set help ( i think )

Cheers,
James


On Mon, Mar 10, 2014 at 2:43 AM, Andrew Lau <andrew at andrewklau.com> wrote:
> Thanks again James!
>
> So far so good, I plan to test this a little more in a few days but so far
> it seems the only volume setting I need is:
> cluster.server-quorum-type: server
>
> Default cluster.server-quorum-ratio >50%
> So 2 is greater than 1.5.. which should allow writes.
>
> On Thu, Mar 6, 2014 at 5:00 PM, James <purpleidea at gmail.com> wrote:
>>
>> Top posting sorry:
>>
>> Yes, you can add a third "arbiter" node, that exists to help with the
>> quorum issues. AFAICT, all you do is peer is with the cluster (as you
>> did with the other hosts) but don't add any storage for example.
>>
>> Then you set the cluster.quorum* style volume settings that you're
>> interested. I don't have a list of exactly which ones off the top of
>> my head, but if you make a list, let me know!
>>
>> Cheers,
>> James
>>
>>
>> On Wed, Mar 5, 2014 at 10:51 PM, Andrew Lau <andrew at andrewklau.com> wrote:
>> > Hi,
>> >
>> > I'm looking for an option to add an arbiter node to the gluster
>> > cluster, but the leads I've been following seem to lead to
>> > inconclusive results.
>> >
>> > The scenario is, a 2 node replicated cluster. What I want to do is
>> > introduce a fake host/arbiter node which would set the cluster to a 3
>> > node meaning, we can meet the conditions of allow over 50% to write
>> > (ie. 2 can write, 1 can not).
>> >
>> > elyograg from IRC gave me a few links [1], [2]
>> > But these appear to be over a year old, and still under review.
>> >
>> > Gluster 3.2 volume options (I'm running 3.4, but there doesn't seem to
>> > be an updated page) [3]
>> > seem to state the that the cluster quorum is identified by active
>> > peers. This also backs up the statement in [2] in regards to a patch
>> > for active volumes rather than cluster peers.
>> >
>> > Has anyone gone down this path, or could they confirm any of these
>> > leads? (ie. does a host w/o any volumes get considered as a peer
>> > within the cluster)
>> >
>> > Thanks,
>> > Andrew
>> >
>> > [1] https://bugzilla.redhat.com/show_bug.cgi?id=914804
>> > [2] http://review.gluster.org/#/c/4363/
>> > [3]
>> > http://gluster.org/community/documentation/index.php/Gluster_3.2:_Setting_Volume_Options#cluster.quorum-type
>> > _______________________________________________
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>> > Gluster-users at gluster.org
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>
>