Re: Expanding Volumes and Geo-replication

Paul Mc Auley <lists@xxxxxxxxx> · Thu, 04 Sep 2014 11:01:03 +0100



    On 04/09/2014 09:24, M S Vishwanath
      Bhat wrote:

    
      On 04/09/14 00:33, Vijaykumar Koppad
        wrote:

      
            On Wed, Sep 3, 2014 at 8:20 PM, M S
              Vishwanath Bhat <vbhat@xxxxxxxxxx> wrote:

              
                On 01/09/14 23:09, Paul Mc Auley wrote:

                   
                    Is geo-replication from a replica 3 volume to a
                    replica 2 volume possible?

                  
                Yes. geo-replication just needs two gluster volumes
                (master -> slave). It doesn't matter what
                configuration master and slave has. But slave should be
                big enough to have all the data in master.
                

                    Should I stop geo-replication before adding
                    additional bricks? (I assume yes)

                  
                There is no need to stop geo-rep while adding more
                bricks to the volume.
                

                    Should I stop the volume(s) before adding additional
                    bricks? (Doesn't _seem_ to be the case)

                  
                No.
                

                    Should I rebalance the volume(s) after adding the
                    bricks?

                  
                Yes. After add-brick, rebalance should be run.
                

                    Should I need to recreate the geo-replication to
                    push-pem subsequently, or can I do that out-of-band?

                    ...and if so should I have to add the passwordless
                    SSH key back in? (As opposed to the restricted
                    secret.pem)

                    For that matter in the inital setup is it an
                    expected failure mode that the initial
                    geo-replication create will fail if the slave host's
                    SSH key isn't known?

                  
                After the add-brick, the newly added node will not have
                any pem files. So you need to do "geo-rep create
                push-pem force". This will actually push the pem files
                to the newly added node as well. And then you need to do
                "geo-rep start force" to start the gsync processes in
                newly added node.

                
                So the sequence of steps for you will be,

                
                1. Add new nodes to both master and slave using gluster
                add-brick command.

              
              After this, we need to run  "gluster system:: execute
                gsec_create " on master node and then proceed with step
                2.
            
          
      Yeah. Missed it... Sorry :)

    
    Ah, I suspect that's the step I was missing.

     The pem
      files needs to be generated for the newly added nodes before
      pushing them to slave. Above command does that.

      
               2.
                Run geo-rep create push-pem force and start force.

                3. Run rebalance.

                
                Hope this works and hope it helps :)

              
    Thanks for that folks, additionally I had assumed I'd need to stop
    the replication before rebalancing or redoing the replication. It
    appears to be a bit more stable if I proceed as described.

    Also my read is that while replication between the master and slave
    is between individual nodes which happen to host single bricks, that
    master doesn't deal with the slave's bricks.

        Paul

  
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