On 8 September 2014 05:05, Krishnan Parthasarathi <kpart...@redhat.com> wrote:
> > > > Bulk of current GlusterD code deals with keeping the configuration of the > > cluster and the volumes in it consistent and available across the nodes. > The > > current algorithm is not scalable (N^2 in no. of nodes) and doesn't > prevent > > split-brain of configuration. This is the problem area we are targeting > for > > the first phase. > > > > As part of the first phase, we aim to delegate the distributed > configuration > > store. We are exploring consul [1] as a replacement for the existing > > distributed configuration store (sum total of /var/lib/glusterd/* across > all > > nodes). Consul provides distributed configuration store which is > consistent > > and partition tolerant. By moving all Gluster related configuration > > information into consul we could avoid split-brain situations. > > Did you get a chance to go over the following questions while making the > > decision? If yes could you please share the info. > > What are the consistency guarantees for changing the configuration in > case of > > network partitions? > > specifically when there are 2 nodes and 1 of them is not reachable? > > consistency guarantees when there are more than 2 nodes? > > What are the consistency guarantees for reading configuration in case of > > network partitions? > > consul uses Raft[1] distributed consensus algorithm internally for > maintaining > consistency. The Raft consensus algorithm is proven to be correct. I will > be > going through the workings of the algorithm soon. I will share my answers > to > the above questions after that. Thanks for the questions, it is important > for the user to understand the behaviour of a system especially under > failure. > I am considering adding a FAQ section to this proposal, where questions > like the above would > go, once it gets accepted and makes it to the feature page. > > [1] - > https://ramcloud.stanford.edu/wiki/download/attachments/11370504/raft.pdf > > The following article provides some results on how Consul works following partitioning, actually testing whether it recovers successfully: http://aphyr.com/posts/316-call-me-maybe-etcd-and-consul It gives Consul a positive review. HTH ~KP > > _______________________________________________ > Gluster-users mailing list > gluster-us...@gluster.org > http://supercolony.gluster.org/mailman/listinfo/gluster-users > -- Jonathan Barber <jonathan.bar...@gmail.com>
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