Gluster users - Jul 2016 - Expand distributed replicated volume

On Tue, Jul 12, 2016 at 4:17 PM, Gandalf Corvotempesta <
gandalf.corvotempesta at gmail.com> wrote:
> 2016-07-12 12:43 GMT+02:00 Pranith Kumar Karampuri <pkarampu at
redhat.com>:
> > True. But at the end of 4 replace-bricks, you have 4 bricks from
earlier
> > configuration which are empty now, which can be re-used. So
essentially
> you
> > have 6 empty bricks which can be put back into use, but these can be
> used to
> > form replica sets as they are not from same machine. So you add-brick
2
> > replica sets with these 6 bricks and do rebalance. Makes sense?
>
> No, it does not make sense.
> I add a new server with some bricks. I have to replace the existing
> one with the newer ones.
> Now, If I try to re-add the "replaced" bricks, is the same like
adding
> directly the new bricks.
>
> If I can't add a bricks from a new single server to a replica3, why
> can I add re-add bricks from an older single server ? That's the same.
>
For adding new bricks into a replica set you need each brick in the replica
set to be from different machine. So you can't add all bricks directly from
just one machine. So how do you get the extra bricks that can be combined
with the bricks on new machine? From old servers. How do you get those?
Using replace-brick. I hope with this info if you can go through the
example once again, it probably may clarify your doubts. Please feel free
to ask any questions you may have.


PS: This discussion proves this functionality definitely goes into heketi
so that we don't have to do all this math. Thanks a lot for bringing this
to our notice!!


-- 
Pranith
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2016-07-12 12:56 GMT+02:00 Pranith Kumar Karampuri <pkarampu at
redhat.com>:
> For adding new bricks into a replica set you need each brick in the replica
> set to be from different machine. So you can't add all bricks directly
from
> just one machine. So how do you get the extra bricks that can be combined
> with the bricks on new machine? From old servers. How do you get those?
> Using replace-brick. I hope with this info if you can go through the
example
> once again, it probably may clarify your doubts. Please feel free to ask
any
> questions you may have.
I'm new to gluster, so let me try to explain and sorry for my dump question.

If I have a replica made with:

(s1b1, s2b1, s3b1)
(s1b2, s2b2, s3b2)
(s1b3, s2b3, s3b3)

Why I cant add a new server getting this result:

(s1b1, s2b1, s3b1, s4b1)
(s1b2, s2b2, s3b2, s4b2)
(s1b3, s2b3, s3b3, s4b3)

?? In this case , I've added a new server with 3 bricks.