[Gluster-devel] query about a split-brain problem found in glusterfs3.12.3

Thu Feb 8 07:38:52 UTC 2018

Hi,
I check the link you provided. It does not mention the the "dirty" attribute, if I try to fix this split-brain by manually setfattr command, should I only set the "trusted.afr.export-client-0" command?
By the way, I feel it is quite strange that the output of "gluster volume heal export info" command there is two entries with the same name, how does this happen?
gluster volume heal export info
Brick sn-0.local:/mnt/bricks/export/brick
Status: Connected
Number of entries: 0

Brick sn-1.local:/mnt/bricks/export/brick
/testdir - Is in split-brain

/testdir - Possibly undergoing heal

Status: Connected
Number of entries: 2

I also do some other test, when sn-0 side file/dir does not has "dirty" and "trusted.afr.export-client-*" attribute and sn-1 side file/dir has both "dirty" and "trusted.afr.export-client-*" non-zero. The gluster could self heal such scenario. But in this case the it could never self heal.

From: Ravishankar N [mailto:ravishankar at redhat.com]
Sent: Thursday, February 08, 2018 11:56 AM
To: Zhou, Cynthia (NSB - CN/Hangzhou) <cynthia.zhou at nokia-sbell.com>; Gluster-devel at gluster.org
Subject: Re: query about a split-brain problem found in glusterfs3.12.3

On 02/08/2018 07:16 AM, Zhou, Cynthia (NSB - CN/Hangzhou) wrote:
Hi,
Thanks for responding?
If split-brain happen in such kind of test is reasonable, how to fix this split-brain situation?

If you are using replica 2, then there is no prevention. Once they occur, you can resolve them using http://docs.gluster.org/en/latest/Troubleshooting/resolving-splitbrain/

If you want to prevent split-brain, you would need to use replica 3 or arbiter volume.

Regards,
Ravi

From: Ravishankar N [mailto:ravishankar at redhat.com]
Sent: Thursday, February 08, 2018 12:12 AM
To: Zhou, Cynthia (NSB - CN/Hangzhou) <cynthia.zhou at nokia-sbell.com><mailto:cynthia.zhou at nokia-sbell.com>; Gluster-devel at gluster.org<mailto:Gluster-devel at gluster.org>
Subject: Re: query about a split-brain problem found in glusterfs3.12.3

On 02/07/2018 10:39 AM, Zhou, Cynthia (NSB - CN/Hangzhou) wrote:

Hi glusterfs expert:
       Good day.
       Lately, we meet a glusterfs split brain problem in our env in /mnt/export/testdir. We start 3 ior process (IOR tool) from non-sn nodes, which is creating/removing files repeatedly in testdir. then we reboot sn nodes(sn0 and sn1) by sequence. Then we meet following problem.
    Do you have some comments on how this could happen? And how to fix it in this situation? Thanks!

Is the problem that split-brain is happening? Is this a replica 2 volume? If yes, then it looks like it is expected behavior?
Regards
Ravi

gluster volume heal export info
Brick sn-0.local:/mnt/bricks/export/brick
Status: Connected
Number of entries: 0

Brick sn-1.local:/mnt/bricks/export/brick
/testdir - Is in split-brain

/testdir - Possibly undergoing heal

Status: Connected
Number of entries: 2

wait for a while .....

gluster volume heal export info
Brick sn-0.local:/mnt/bricks/export/brick
Status: Connected
Number of entries: 0

Brick sn-1.local:/mnt/bricks/export/brick
/testdir - Possibly undergoing heal

/testdir - Possibly undergoing heal

and finally:

[root at sn-0:/root<http://sn-0/root>]
# gluster v heal export info
Brick sn-0.local:/mnt/bricks/export/brick<http://local/mnt/bricks/export/brick>
Status: Connected
Number of entries: 0

Brick sn-1.local:/mnt/bricks/export/brick<http://local/mnt/bricks/export/brick>
/testdir - Is in split-brain

Status: Connected
Number of entries: 1

[root at sn-0:/root<http://sn-0/root>]

# getfattr -m .* -d -e  hex /mnt/bricks/export/brick/testdir

getfattr: Removing leading '/' from absolute path names

# file: mnt/bricks/export/brick/testdir

trusted.gfid=0x5622cff893b3484dbdb6a20a0edb0e77

trusted.glusterfs.dht=0x000000010000000000000000ffffffff

[root at sn-1:/root<http://sn-1/root>]

# getfattr -m .* -d -e  hex /mnt/bricks/export/brick/testdir

getfattr: Removing leading '/' from absolute path names

# file: mnt/bricks/export/brick/testdir

trusted.afr.dirty=0x000000000000000000000001

trusted.afr.export-client-0=0x000000000000000000000038

trusted.gfid=0x5622cff893b3484dbdb6a20a0edb0e77

trusted.glusterfs.dht=0x000000010000000000000000ffffffff

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