[Bugs] [Bug 1255698] New: Write performance from a Windows client on 3-way replicated volume decreases substantially when one brick in the replica set is brought down

Fri Aug 21 11:06:14 UTC 2015

https://bugzilla.redhat.com/show_bug.cgi?id=1255698

            Bug ID: 1255698
           Summary: Write performance from a Windows client on 3-way
                    replicated volume decreases substantially when one
                    brick in the replica set is brought down
           Product: GlusterFS
           Version: 3.7.3
         Component: replicate
          Keywords: Triaged
          Assignee: bugs at gluster.org
          Reporter: ravishankar at redhat.com
                CC: bengland at redhat.com, bugs at gluster.org,
                    gluster-bugs at redhat.com, jharriga at redhat.com,
                    mpillai at redhat.com
        Depends On: 1227759, 1250170
            Blocks: 1216951, 1223636

Description of problem:
-------------------------

On a 3-way replicated volume mounted on a Windows client, one of the bricks was
brought down. The write speed observed while copying a .iso file was
substantially reduced as compared to the speeds observed with all bricks in the
replica set being up.

See results of the copy operations below -

With all 3 bricks up
--------------------

PS Z:\> robocopy C:\Users\shruti\Downloads\test Z:\ RHS.iso

------------------------------------------------------------------------
   ROBOCOPY     ::     Robust File Copy for Windows
------------------------------------------------------------------------

  Started : Wed Jun 03 16:36:45 2015

   Source : C:\Users\shruti\Downloads\test\
     Dest : Z:\

    Files : RHS.iso

  Options : /COPY:DAT /R:1000000 /W:30

------------------------------------------------------------------------

                           1    C:\Users\shruti\Downloads\test\
100%        New File               1.5 g        RHS.iso

------------------------------------------------------------------------

               Total    Copied   Skipped  Mismatch    FAILED    Extras
    Dirs :         1         0         1         0         0         0
   Files :         1         1         0         0         0         0
   Bytes :   1.566 g   1.566 g         0         0         0         0
   Times :   0:01:21   0:01:21                       0:00:00   0:00:00

   Speed :            20750024 Bytes/sec.
   Speed :            1187.325 MegaBytes/min.

   Ended : Wed Jun 03 16:38:06 2015

With one brick in replica set brought down
-------------------------------------------

PS Z:\> robocopy C:\Users\shruti\Downloads\test Z:\ RHS.iso

-------------------------------------------------------------------------------
   ROBOCOPY     ::     Robust File Copy for Windows
-------------------------------------------------------------------------------

  Started : Wed Jun 03 16:39:38 2015

   Source : C:\Users\shruti\Downloads\test\
     Dest : Z:\

    Files : RHS.iso

  Options : /COPY:DAT /R:1000000 /W:30

------------------------------------------------------------------------------

                           1    C:\Users\shruti\Downloads\test\
100%        New File               1.5 g        RHS.iso

------------------------------------------------------------------------------

               Total    Copied   Skipped  Mismatch    FAILED    Extras
    Dirs :         1         0         1         0         0         0
   Files :         1         1         0         0         0         0
   Bytes :   1.566 g   1.566 g         0         0         0         0
   Times :   0:03:26   0:03:26                       0:00:00   0:00:00

   Speed :             8158524 Bytes/sec.
   Speed :             466.834 MegaBytes/min.

   Ended : Wed Jun 03 16:43:05 2015

Such a drop in performance is not observed with a 2-way replicated volume in
the same setup.

Version-Release number of selected component (if applicable):
----------------------------------------------------------------
glusterfs-3.7.0-3.el6rhs.x86_64
samba-4.1.17-7.el6rhs.x86_64

How reproducible:
------------------
100%

Steps to Reproduce:
--------------------
1. Created a 6x3 volume and mounted on a Windows 7 client machine.
2. Copied a .iso file from the Windows local drive to the gluster share.
3. Brought down one brick of the replica set and ran the copy operation again.

Actual results:
-----------------

There is a significant drop in write speeds when results from step 3 are
compared to results from step 2. Write speed with one brick down reduce to
roughly 40% of the speed observed with all bricks up.

Expected results:
------------------

Expected behaviour is that write speed should not be affected if one brick in a
replica set is down.

--- Additional comment from Ravishankar N on 2015-08-04 12:09:36 EDT ---

Patch: http://review.gluster.org/#/c/11827/

--- Additional comment from Anand Avati on 2015-08-05 13:00:35 EDT ---

REVIEW: http://review.gluster.org/11827 (afr: modify afr_txn_nothing_failed())
posted (#2) for review on master by Ravishankar N (ravishankar at redhat.com)

--- Additional comment from Ben England on 2015-08-09 21:33:50 EDT ---

adding perf team members to cc list

Referenced Bugs:

https://bugzilla.redhat.com/show_bug.cgi?id=1223636
[Bug 1223636] 3.1 QE Tracker
https://bugzilla.redhat.com/show_bug.cgi?id=1227759
[Bug 1227759] Write performance from a Windows client on 3-way replicated
volume decreases substantially when one brick in the replica set is brought
down
https://bugzilla.redhat.com/show_bug.cgi?id=1250170
[Bug 1250170] Write performance from a Windows client on 3-way replicated
volume decreases substantially when one brick in the replica set is brought
down
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