www.nico.schottelius.org/blog/how-to-access-gluster-from-multiple-networks.mdwn

[[!meta title="How to access gluster from multiple networks"]]

# TL;DR

Create volumes name based instead of IP based:

    gluster volume create xfs-plain replica 2 transport vmhost1:/home/gluster vmhost2:/home/gluster 

instead of

    gluster volume create xfs-plain replica 2 transport 192.168.0.1:/home/gluster 192.168.0.2:/home/gluster 
And have the names point to different IP addresses.

## The setup

The basic setup (in our case) looks like this:


    ---------------------------------
    | Clients / Users               |
    ---------------------------------
            |
            |
    ---------------------------------       ---------------------------------
    | frontend (with opennebula)    |    ---| vmhost1 with glusterfs        |
    ---------------------------------   /   ---------------------------------
            |                          / eth0                       eth1
            |-------------------------<                              ||
                                       \ eth0                       eth1
                                        \   ---------------------------------
                                         ---| vmhost2 with glusterfs        |
                                            ---------------------------------


The frontend running [[!opennebula]] connects to 
**vmhost1** and **vmhost2** using their public interfaces.

The gluster bricks running on the vm hosts are supposed to communicate
via eth1, so that the traffic for [[!gluster]] does not influence
the traffic of the virtual machines to the Internet. The gluster filesystem
of the vmhosts is only thought to be used by the virtual machines running
on those two hosts - an isolated cluster. Thus the volume initially has been created
like this:

    gluster volume create xfs-plain replica 2 transport 192.168.0.1:/home/gluster 192.168.0.2:/home/gluster 

## The problem

However, the frontend requires access to the gluster volume, because
[[!opennebula]] needs to copy and import the VM image into the gluster
datastore. Even though the *glusterd* process listens on any IP address,
the volume contains the information that it runs on 192.168.0.1
and 192.168.0.2 and is thus not reachable from the frontend.

## Using name based volumes

The frontend can reach the vm hosts via **vmhost1** and **vmhost2**,
which resolves to their **public IP addresses** via DNS.

On the vm hosts we created entries in **/etc/hosts** using [[!cdist]]
that looks as following:

    192.168.0.1 vmhost1
    192.168.0.2 vmhost2

Now we re-created the volume using

    gluster volume create xfs-plain replica 2 transport tcp vmhost1:/home/gluster vmhost2:/home/gluster 
    gluster volume start xfs-plain

And it correctly shows up in the volume info:

    %gluster volume info
    Volume Name: xfs-plain
    Type: Replicate
    Volume ID: fe45c626-c79d-4e67-8f19-77938470f2cf
    Status: Started
    Number of Bricks: 1 x 2 = 2
    Transport-type: tcp
    Bricks:
    Brick1: vmhost1-cluster1.place4.ungleich.ch:/home/gluster
    Brick2: vmhost2-cluster1.place4.ungleich.ch:/home/gluster

And now we can mount it successfully on the frontend using

    % mount -t glusterfs  vmhost2:/xfs-plain /mnt/gluster

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[[!tag gluster filesystem unix ungleich]]