[Gluster-users] Expanding Volumes and Geo-replication

[Vijaykumar Koppad]

On Wed, Sep 3, 2014 at 8:20 PM, M S Vishwanath Bhat <vbhat at redhat.com>
wrote:

> On 01/09/14 23:09, Paul Mc Auley wrote:
>
>> Hi Folks,
>>
>> Bit of a query on the process for setting this up and the best practices
>> for same.
>>
>> I'm currently working with a prototype using 3.5.2 on vagrant and I'm
>> running into assorted failure modes with each pass.
>>
>> The general idea is I start with two sites A and B where A has 3 bricks
>> used to build a volume vol at replica 3 and
>> B has 2 bricks with at replica 2 to also build vol.
>> I create 30 files is A::vol and then set up geo-replication from A to B
>> after which I verify that the files have appeared in B::vol.
>> What I want to do then is double the size of volumes (presumably growing
>> one and not the other is a bad thing)
>> by adding 3 bricks to A and 2 bricks to B.
>>
>> I've had this fail number of ways and so I have a number of questions.
>>
>> Is geo-replication from a replica 3 volume to a replica 2 volume possible?
>>
> Yes. geo-replication just needs two gluster volumes (master -> slave). It
> doesn't matter what configuration master and slave has. But slave should be
> big enough to have all the data in master.
>
>  Should I stop geo-replication before adding additional bricks? (I assume
>> yes)
>>
> There is no need to stop geo-rep while adding more bricks to the volume.
>
>  Should I stop the volume(s) before adding additional bricks? (Doesn't
>> _seem_ to be the case)
>>
> No.
>
>  Should I rebalance the volume(s) after adding the bricks?
>>
> Yes. After add-brick, rebalance should be run.
>
>  Should I need to recreate the geo-replication to push-pem subsequently,
>> or can I do that out-of-band?
>> ...and if so should I have to add the passwordless SSH key back in? (As
>> opposed to the restricted secret.pem)
>> For that matter in the inital setup is it an expected failure mode that
>> the initial geo-replication create will fail if the slave host's SSH key
>> isn't known?
>>
> After the add-brick, the newly added node will not have any pem files. So
> you need to do "geo-rep create push-pem force". This will actually push the
> pem files to the newly added node as well. And then you need to do "geo-rep
> start force" to start the gsync processes in newly added node.
>
> So the sequence of steps for you will be,
>
> 1. Add new nodes to both master and slave using gluster add-brick command.
>
After this, we need to run  "gluster system:: execute gsec_create " on
master node and then proceed with step 2.

> 2. Run geo-rep create push-pem force and start force.
> 3. Run rebalance.
>
> Hope this works and hope it helps :)
>
>
> Best Regards,
> Vishwanath
>
>
>
>> Thanks,
>>     Paul
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>
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