[Gluster-users] Problem adding brick to an existing volume

[Oliver]

Hi Gluster Users,

I am hoping that someone can help me put me on the right track maybe ..

Objective is to have a high available, extensible storage cluster with a 
fair rate of redundancy.

I was thinking of a cluster of multiple machines, starting with 2 
servers, 2 disks each and a config of

Volume Name: originals
Type: Distributed-Replicate
Volume ID: xx
Status: Started
Number of Bricks: 2 x 2 = 4
Transport-type: tcp

Volume: originals
Brick srv1:/srv/vol1 (/dev/sdb1 500GB)
Brick srv1:/srv/vol2 (/dev/sdc1 500GB)
Brick srv2:/srv/vol1 (/dev/sdb1 500GB)
Brick srv2:/srv/vol2 (/dev/sdb1 500GB)

Now I would like to add another server with JUST 1 500GB disk, peer 
probe and everything is fine so far, but when it comes to adding the brick:

root at srvdst01:~# gluster volume add-brick videos srv3:/srv/vol1
volume add-brick: failed: Incorrect number of bricks supplied 1 with count 2

Ok, trying to change the num of replica's or whatever just results in

root at srvdst01:~# gluster volume add-brick videos replica 3 
srv3:/srv/vol1 (or vol3 or vol4, this doesnt matter)
volume add-brick: failed: Operation failed

No way to get around this .. What do I have to do ? Add two bricks in 1 
command ? How would it work in the future when I gets to production 
machines with each 2 or even more disks ?

Were great someone could gimme a hint.

Its gluster 3.4.2-1ubuntu1 amd64 on ubuntu 14.04 LTS.

regards, Oliver