Re: Cluster is empty but it still use 1Gb of data

Gonzalo Aguilar Delgado <gaguilar@xxxxxxxxxxxxxxxxxx> · Fri, 2 Mar 2018 12:18:21 +0100



    Hi Max, 

    
    No that's not normal. 9GB for an empty cluster. Maybe you
      reserved some space or you have other service that's taking the
      space. But It seems way to much for me.

    
    El 02/03/18 a las 12:09, Max Cuttins
      escribió:

    
      I don't care of get back those space.

        I just want to know if it's expected or not.

        Because I run several rados bench with the flag --no-cleanup
      And maybe I leaved something in the way.

      
      Il 02/03/2018 11:35, Janne Johansson
        ha scritto:

      
            2018-03-02 11:21 GMT+01:00 Max
              Cuttins <max@xxxxxxxxxxxxx>:

              
                  Hi everybody,
                  i deleted everything from the cluster after some
                    test with RBD.

                    Now I see that there something still in use:
                  
                      data:

                          pools:   0 pools, 0 pgs

                          objects: 0 objects, 0 bytes

                          usage:   9510 MB
                          used, 8038 GB / 8048 GB avail

                          pgs:

                    
                  Is this the overhead of the bluestore journal/wall?

                    Or there is something wrong and this should be zero?

                  
              People setting up new clusters also see this, there
                are overhead items and stuff that eat some space
              so it would never be zero. At your place, it would
                seem it is close to 0.1%, so just live with it and move
              on to using your 8TB for what you really needed it to
                be used for.
              

              In almost no case will I think that "if only I could
                get those 0.1% back and then my cluster would be great
              again".
              

              Storage clusters should probably have something like
                10% "admin" margins so if ceph warns and
              whines at OSDs being 85% full, then at 75% you should
                be writing orders for more disks and/or more
              storage nodes.
              

              At that point, regardless of where the
                "miscalculation" is, or where ceph manages to waste
              9500M while you think it should be zero, it will be
                all but impossible to make anything decent with it
              if you were to get those 0.1% back with some magic
                command.
              

            -- 

            May the most significant
              bit of your life be positive.

            
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