[Gluster-users] Feedback and Questions on afr+unify

[Prabhu Ramachandran]

Hi,

Krishna Srinivas wrote:
>> Interesting, so any existing data on the disks will not be affected? How
>> does that work?  Does this mean I can fill the disks a-priori before
>> unifying them?
> 
> Unify checks with all the subvols on where it is before opening.
> Yes you can have pre-filled data before unifying them.

OK, thanks for the clarification.

>>>>  - What would happen if I added another brick, say another disk to the
>>>> existing set on one of the machines?  Would it break the round-robin
>>>> scheduler that I am using?  I see from the FAQ that this should work with
>>>> the alu but will it work with rr?
>>> ALU will be useful when you add servers later. i.e it will see free
>>> diskspace and schedule creation of new files there. RR will just
>>> round-robin.
>>>
>>> You can experiement with the new "DHT" translator in place of unify.
>> OK, I can do that, I see dht does not need the extra namespace disk, so I
>> guess I can clear out that directory.
> 
> Note that DHT is a separate cluster xlator and not scheduler.

Sorry, I understand and messed up the terminology.

> You are using AFR over unify, The problem is when one of the servers
> on unify goes down AFR will see missing files and recreate them, so
> when the downed server comes back up unify will see those files on two
> subvols.

OK.  So this will persist whether I use dht or unify, right?  So what is 
the way out of this problem.

>>> When you have afr over unify and one of unify subvol goes down, afr's
>>> selfheal will create missing files which you don't want to happen.
>> OK, so you are saying I need to simply switch to using dht, remove the
>> namespace directory and continue with the setup and this problem will not
>> occur?
> 
> No, DHT is not related to this.

OK, sorry to be slow but now I am confused.  What should I do to my 
setup to not face these problems?

Thanks.

cheers,
prabhu