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

[Ravishankar N]

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>; 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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