Re: 3.7 Arbiter and/or quorum

Ravishankar N <ravishankar@xxxxxxxxxx> · Thu, 16 Jul 2015 07:20:07 +0530



    On 07/15/2015 10:54 PM, Scott Harvanek
      wrote:

    
      Using the virt group which does-

      
      cluster.quorum-type: auto

      cluster.server-quorum-type: server

      
      And from my understanding this means that quorum enforcement is
      enabled, and that it's brick related so if I only have two bricks
      then I cannot achieve 51% and split brain is likely even with a
      third node in the pool.  If I move to fixed 1, then the likelihood
      of splitbrain is high.

    
    In a replica 2 setup, if you set cluster.quorum-type to auto, you
    can avoid split-brains in AFR. But the first brick must be up at all
    times.

    -Ravi

    
      So what do I do here, get a fourth node and do distributed
      replicated?  Trying to find the best performance option while
      minimizing split brain potential and I'm stuck with 3.6 clients (
      RHEV-H ) so the aforementioned arbiter is out, Replica 3 just
      seems to be a pig on the client side due to the triple write.

      
      -- 

        Scott H.

        
              Ravishankar N
            
              July
                  15, 2015 at 1:09 PM
          
        
          On 07/15/2015 09:22 PM, Scott Harvanek wrote:
          

          I saw Ravi mention something earlier
            about the new arbiter volumes in 3.7
            

            - Can you run a arbiter 3.7 server volume with 3.6 clients? 
            Or does this not work?
            

          Unfortunately, no. This is because the logic for the feature
          is mostly in the AFR translator which is loaded on the client
          process (with some minor logic in the arbiter translator
          loaded on the brick process). So both clients and servers need
          to be 3.7.
          

          Quorum question -
            

            - 3.6 server and clients, replica 2, however there's three+
            servers in the cluster ( gluster pool list ).  If one of the
            replicas fail is quorum maintained via the other servers in
            the cluster even though they are not part of the volume?
            

          That would depend on what type of quorum is enabled (client or
          server side). Each type has a different impact. You can look
          for the meaning of cluster.quorum-type, cluster.quorum-count
          (these are client side quorum options, applicable only to
          replicate volumes) and cluster.server-quorum-type,
          cluster.server-quorum-ratio (these are server side quorum
          options; they are not specific to replicate volumes) in
          'gluster volume set help`.
          

          HTH,
          

          Ravi
          

              Scott Harvanek
            
              July
                  15, 2015 at 11:52 AM
          
        
        I saw Ravi mention
          something earlier about the new arbiter volumes in 3.7
          

          - Can you run a arbiter 3.7 server volume with 3.6 clients? 
          Or does this not work?
          

          Quorum question -
          

          - 3.6 server and clients, replica 2, however there's three+
          servers in the cluster ( gluster pool list ).  If one of the
          replicas fail is quorum maintained via the other servers in
          the cluster even though they are not part of the volume?
          

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