[Gluster-users] probable cause of read performance issue

[Jules Wang]

 hi, all:
      When I was testing glusterfs performance by iozone with only ONE machine, I got the following chart:

       https://dl.dropbox.com/u/33453649/perf_htm_m19da4047.jpg

     Y axis represent disk throughput in kb/s. X axis represent  test cases.

     It is obvious that  R+W case has the worst read performance, R+W means you turn on both Read-ahead xlator and Write-behind xlator. Unfortunately, that`s the default configuration of glusterfs.

    Though I run glusterfs only on one machine, I think this result explains something. Maybe you have more insight on it.

    More info:
-------------------------
cmdline: ./iozone -a -n 16g -g 16g -i 0 -i 1 -i 2 -i 3 -f /mnt/iozone -Rb no-rh.xls -y 4096k
CPU: intel  i3-2120  X 4
RAM: 8G
Glusterfs Version:  3.3
Volume info:
Volume Name: abc
Type: Distribute
Volume ID: 6e0104f1-d32a-4ed4-b011-d29ccf27abe1
Status: Started
Number of Bricks: 1
Transport-type: tcp
Bricks:
Brick1: 10.1.82.224:/abc
Options Reconfigured:
performance.io-cache: off
performance.quick-read: off
performance.read-ahead: on
performance.write-behind: on
--------------------------------------------

Best Regards.
Jules Wang.
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