Re: Gluster performance on the small files

Joe Julian <joe@xxxxxxxxxxxxxxxx> · Mon, 16 Feb 2015 12:32:31 -0800



    On 02/12/2015 10:58 PM, Punit Dambiwal
      wrote:

    
      Hi,
        

        I have seen the gluster performance is dead slow on the
          small files...even i am using the SSD....it's too bad
          performance....even i am getting better performance in my SAN
          with normal SATA disk...
        

        I am using distributed replicated glusterfs with replica
          count=2...i have all SSD disks on the brick...
        

          root@vm3:~#
              dd bs=64k count=4k
              if=/dev/zero of=test oflag=dsync
          4096+0
              records in
          4096+0
              records out
          268435456
              bytes (268 MB) copied, 57.3145
              s, 4.7 MB/s
          

          root@vm3:~#
              dd bs=64k count=4k
              if=/dev/zero of=test conv=fdatasync
          4096+0
              records in
          4096+0
              records out
          268435456
              bytes (268 MB) copied, 1.80093
              s, 149 MB/s
          

    How small is your VM image? The image is the file that GlusterFS is
    serving, not the small files within it. Perhaps the filesystem
    you're using within your VM is inefficient with regard to how it
    handles disk writes.

    
    I believe your concept of "small file" performance is misunderstood,
    as is often the case with this phrase. The "small file" issue has to
    do with the overhead of finding and checking the validity of any
    file, but with a small file the percentage of time doing those
    checks is proportionally greater. With your VM image, that file is
    already open. There are no self-heal checks or lookups that are
    happening in your tests, so that overhead is not the problem.

  
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