Need help in understanding volume heal-info behavior

Chalcogen <chalcogen_eg_oxygen@xxxxxxxxx> · Mon, 28 Apr 2014 01:30:19 +0530



    Hi everyone,

      
      I have trouble understanding the following behavior:

      
      Suppose I have a replica 2 volume 'testvol' on two servers,
      server1 and server2, composed of server1:/bricks/testvol/brick and
      server2:/bricks/testvol/brick. Also, suppose it contains a good
      number of files.

      
      Now, assume I remove one of the two bricks, as:

    
    root@server1~# gluster volume remove-brick testvol replica 1
    server1:/bricks/testvol/brick

    
      Now, I unmount and delete the logical volume supporting the brick
      and then recreate it (with a different size), and mount it the
      same way as it was mounted before (at /brick/testvol/). Then, I
      re-add it as:

    
    root@server1~# gluster volume add-brick testvol replica 2
    server1:/bricks/testvol/brick

    
      I observe that the brick on server1 does not contain any of the
      data that was in the volume.

    
    root@server1~# ls /bricks/testvol/brick

    root@server1~# 

    
    This is all right by me, since glusterfs needs
      some time to discover and sync files that are absent on the brick
      of server1. In fact, if I leave the setup undisturbed for 15
      minutes to half an hour, I find that all data appears within the
      brick of server1, just as you would expect. Also, if I wish to
      speed up the process, I simply do a ls -Ra on the directory where
      the volume is mounted, and all files sync onto server1's brick.
      This is also very much as expected.

      
      However, during the period where data on server1's brick is not
      available, if you query the heal info for the volume, gluster cli
      reports that 'Number of entries' is '0', and that too all of
      'info', 'heal-failed', and 'split-brain'. This is what becomes a
      bit of a trouble for me. Fact is, we are attempting to automate
      the monitoring of our glusterfs volumes, and we depend upon heal
      info alone to decide whether data on server1 and server2 are in
      sync. 

      
      Could somebody, therefore, help me with the following questions?

      a) Which files exactly show up in heal info?

      b) What exactly should I look to monitor if we are to ascertain
      that data on our servers are in sync?

      
      Thanks a lot for your responses!

    
      Anirban

      
      P.s. I am using glusterfs 3.4.2 over linux kernel version 2.6.34.

    
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