Re: Add single server

Joe Julian <joe@xxxxxxxxxxxxxxxx> · Mon, 1 May 2017 13:39:19 -0700



    On 05/01/2017 11:55 AM, Pranith Kumar
      Karampuri wrote:

    
          On Tue, May 2, 2017 at 12:20 AM,
            Gandalf Corvotempesta <gandalf.corvotempesta@xxxxxxxxx>
            wrote:

            2017-05-01 20:43 GMT+02:00 Shyam <srangana@xxxxxxxxxx>:

                > I do agree that for the duration a brick is
                replaced its replication count

                > is down by 1, is that your concern? In which case I
                do note that without (a)

                > above, availability is at risk during the
                operation. Which needs other

                > strategies/changes to ensure tolerance to
                errors/faults.

                
              Oh, yes, i've forgot this too.

              
              I don't know Ceph, but Lizard, when moving chunks across
              the cluster,

              does a copy, not a movement

              During the whole operation you'll end with some
              files/chunks

              replicated more than the requirement.

            
            Replace-brick as a command is implemented with the goal
              of replacing a disk that went bad. So the availability was
              already less. In 2013-2014 I proposed that we do it by
              adding brick to just the replica set and increase its
              replica-count just for that set once heal is complete we
              could remove this brick. But at the point I didn't see any
              benefit to that approach, because availability was already
              down by 1. But with all of this discussion it seems like a
              good time to revive this idea. I saw that Shyam suggested
              the same in the PR he mentioned before.

            
    I've always been against the idea of being a replica down based on
    that supposition. I've never had to replace-brick because a brick
    failed. It's always been for reconfiguration reasons. Good
    monitoring and analysis can predict drive failures in plenty of time
    to replace a functioning brick.

    
              If you have a replica 3, during the movement, some file
              get replica 4

              In Gluster the same operation will bring you replica 2.

              
              IMHO, this isn't a viable/reliable solution

              
              Any change to change "replace-brick" to increase the
              replica count

              during the operation ?

            
          It can be done. We just need to find time to do this.

        
          -- 

          
            Pranith

            
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