[Gluster-devel] about split-brain

[Ravishankar N]

On 08/21/2014 08:23 AM, everybody_enjoy at 163.com wrote:
>
> hi all:
>
> I have a problem about split-brain, details as below:
>
> PC1 and PC2 is AFR, stored a file 1.txt
>
> 1. write "123" to 1.txt, then 1.txt in pc1 is same with 1.txt in PC2, 
> content is "123"
>
> 2. PC1  network disconnect, write "45" to 1.txt, then  content of 
> 1.txt in pc1 is "123",
> content of 1.txt in pc2 is "12345"
>
> 3. PC2  network disconnect, but PC1 network is good, write "67" to 
> 1.txt, then  content of 1.txt in pc1 is "12367",
> content of 1.txt in pc1 is "12345"
>
> 4. so split brain occur
>
> is this a bug or design this?
>

The steps you have described is exactly how data split-brain occurs.

> how glusterfs avoid this? Have some ways to solve? this is my 
> questions. thank you
>

As of today, glusterfs gives EIO (input/output error) when you try to 
access a split-brained file. You need to resolve the split-brain [1] 
before the file becomes accessible again. If you want to *avoid* 
split-brain, you need to enable quorum [2].

[1] https://github.com/gluster/glusterfs/blob/master/doc/split-brain.md
[2] 
https://access.redhat.com/documentation/en-US/Red_Hat_Storage/2.1/html/Administration_Guide/ch10s10.html
https://access.redhat.com/documentation/en-US/Red_Hat_Storage/2.0/html/Administration_Guide/sect-User_Guide-Managing_Volumes-Quorum.html

Hope this helps.

>
> ------------------------------------------------------------------------
> everybody_enjoy at 163.com
>
>
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