[Gluster-users] ... i was able to produce a split brain...

Ted Miller tmiller at sonsetsolutions.org
Tue Feb 3 19:56:51 UTC 2015

On 2/3/2015 2:44 PM, Joe Julian wrote:
> On 02/03/2015 11:34 AM, Ted Miller wrote:
>> On 2/3/2015 12:23 PM, Joe Julian wrote:
>>>> ****************************************************************
>>>> That brought another thought to mind (have not had reason to try it):
>>>> How does gluster cope if you go behind its back and rename a "rejected" 
>>>> file?  For instance, in my example above, what if I go directly on the 
>>>> brick and rename the host-2 copy of the file to hair-pulling.txt-dud?  
>>>> The ideal scenario would seem to be that if user does a heal it would 
>>>> treat the copy as new file, see no dupe for hair-pulling.txt, and create 
>>>> a new dupe on host-2.  Since hair-pulling.txt-dud is also a new file, a 
>>>> dupe would be created on host-1.  User could then access files, verify 
>>>> correctness, and then delete hair-pulling.txt-dud.
>>> This should cause you to have two files with the same gfid. This will 
>>> create the hardlink in .glusterfs again, and the heal will then re-create 
>>> the .txt file also with that same gfid. Since both files will have the 
>>> same gfid (stored in extended attributes) and be hard linked to the same 
>>> file under .glusterfs you should then end up with both files being 
>>> split-brain. 
>> Joe, I moved you comments up to be closest to the proposal they seem 
>> relevant to.
>>>> *****************************************************************
>>>> A not-officially-sanctioned way that I dealt with a split-brain a few 
>>>> versions back:
>>>> 1. decided I wanted to keep file on host-2
>>>> 2. log onto host-2
>>>> 3. cp /brick/data1/hair-pulling.txt /gluster/data1/hair-pulling.txt-dud
>>>> 4. rm /brick/data1/hair-pulling.txt
>>>> 5. follow some Joe Julian blog stuff to delete the "invisible fork" of file
>>>> 6. gluster volume heal data1 all
>> If you note, in the above scenario _I copied from the brick to the mounted 
>> gluster volume_.  I believe that this forces the breaking of any linkage 
>> between the old file and the new one.  Am I missing something there?
> Yep, I missed that. I seem to be suffering from split-brain, myself, today.
Don't sweat it, your blog posts have dug me out of more than one hole.

Ted Miller
Elkhart, IN, USA

> .
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