[Gluster-users] Expanding Volumes and Geo-replication

[M S Vishwanath Bhat]

On 04/09/14 00:33, Vijaykumar Koppad wrote:
>
>
>
> On Wed, Sep 3, 2014 at 8:20 PM, M S Vishwanath Bhat <vbhat at redhat.com 
> <mailto: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.
Yeah. Missed it... Sorry :)

The pem files needs to be generated for the newly added nodes before 
pushing them to slave. Above command does that.
>
>     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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