Re: GlusterFS behaviour on stat syscall with relatime activated

Pranith Kumar Karampuri <pkarampu@xxxxxxxxxx> · Fri, 05 Feb 2016 11:24:30 +0530



    On 02/03/2016 10:12 PM, Simon
      Turcotte-Langevin wrote:

    
        Hi, we have multiple
            clusters of GlusterFS which are mostly alike. The typical
            setup is as such:
         
        -         
              Cluster
            of 3 nodes
        -         
              Replication
            factor of 3
        -         
              Each
            node has 1 brick, mounted on XFS with RELATIME and
            NODIRATIME
        -         
              Each
            node has 8 disks in RAID 0 hardware
         
        The main problem we are
            facing is that observation of the access time of a file on
            the volume will update the access time.
         
        The steps to reproduce
            the problem are:
         
        -         
              Create
            a file (echo ‘some data’ > /mnt/gv0/file)
        -         
              Touch
            its mtime and atime to some past date (touch –d 19700101
            /mnt/gv0/file)
        -         
              Touch
            its mtime to the current timestamp (touch –m /mnt/gv0/file)
        -         
              Stat
            the file until atime is updated (stat /mnt/gv0/file)
        
          o  
              Sometimes
            it’s instant, sometimes it requires to execute the above
            command a couple of time
      
    
    atime changes on open call.

    
    Quick-read xlator opens the file and reads the content on 'lookup'
    which gets triggered in stat. It does that to serve reads from
    memory to reduce number of network round trips for small files.
    Could you disable that xlator and try the experiment? On my machine
    the time didn't change after I disabled that feature using:

    
    "gluster volume set <volname> quick-read off"

    
    Pranith

    
        On the IRC channel, I spoke to a developer
            (nickname ndevos) who said that it might be a getxattr()
            syscall that could be called when stat() is called on a
            replicated volume.
         
        Anybody can reproduce this issue? Is it a bug,
            or is it working as intended? Is there any workaround?
         
        Thank you,
        Simon
      
      
      _______________________________________________
Gluster-users mailing list
Gluster-users@xxxxxxxxxxx
http://www.gluster.org/mailman/listinfo/gluster-users
    
    
_______________________________________________
Gluster-users mailing list
Gluster-users@xxxxxxxxxxx
http://www.gluster.org/mailman/listinfo/gluster-users