[Gluster-users] GlusterFS as virtual machine storage

[WK]

On 8/25/2017 2:21 PM, lemonnierk at ulrar.net wrote:
>> This concern me, and it is the reason I would like to avoid sharding.
>> How can I recover from such a situation? How can I "decide" which
>> (reconstructed) file is the one to keep rather than to delete?
>>
> No need, on a replica 3 that just doesn't happen. That's the main
> advantage of it, that and the fact that you can perform operations on
> your servers without having the volume go down.
>
> For a replica 2 though, it will happen. With or without sharding the
> operation is the same, it involves fiddling with gfids and is a bit
> annoying, but not that hard for one file. But with sharding enabled
> you'll need to pick each split brained shard out, which is I imagine a
> huge pain .. Again, just don't do 2 nodes, it's a _bad_ idea. Add at the
> very least an arbiter.
>


Big +1 on what was Kevin just said.  Just avoiding the problem is the 
best strategy.

However, for the record,  and if you really, really want to get deep 
into the weeds on the subject, then the  Gluster people have docs on 
Split-Brain recovery.

https://gluster.readthedocs.io/en/latest/Troubleshooting/split-brain/

and if you Google the topic, there are a lot of other blog posts, 
emails, etc that discuss it.

I'd recommend reviewing those as well to wrap your head around what is 
going on.