=============
Configuration
=============

Configure Firewall
~~~~~~~~~~~~~~~~~~

For the Gluster to communicate within a cluster either the firewalls
have to be turned off or enable communication for each server.

::

        iptables -I INPUT -p all -s `<ip-address>` -j ACCEPT

Configure the trusted pool
~~~~~~~~~~~~~~~~~~~~~~~~~~

Remember that the trusted pool is the term used to define a cluster of
nodes in Gluster. Choose a server to be your “primary” server. This is
just to keep things simple, you will generally want to run all commands
from this tutorial. Keep in mind, running many Gluster specific commands
(like \`gluster volume create\`) on one server in the cluster will
execute the same command on all other servers.

::

        gluster peer probe (hostname of the other server in the cluster, or IP address if you don’t have DNS or /etc/hosts entries)

Notice that running \`gluster peer status\` from the second node shows
that the first node has already been added.

Partition, Format and mount the bricks
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Assuming you have a brick at /dev/sdb:

::

        fdisk /dev/sdb and create a single partition

Format the partition
~~~~~~~~~~~~~~~~~~~~

::

        mkfs.xfs -i size=512 /dev/sdb1

Mount the partition as a Gluster "brick"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

::

        mkdir -p /export/sdb1 && mount /dev/sdb1 /export/sdb1 && mkdir -p /export/sdb1/brick

Add an entry to /etc/fstab
~~~~~~~~~~~~~~~~~~~~~~~~~~

::

        echo "/dev/sdb1 /export/sdb1 xfs defaults 0 0"  >> /etc/fstab

Set up a Gluster volume
^^^^^^^^^^^^^^^^^^^^^^^

The most basic Gluster volume type is a “Distribute only” volume (also
referred to as a “pure DHT” volume if you want to impress the folks at
the water cooler). This type of volume simply distributes the data
evenly across the available bricks in a volume. So, if I write 100
files, on average, fifty will end up on one server, and fifty will end
up on another. This is faster than a “replicated” volume, but isn’t as
popular since it doesn’t give you two of the most sought after features
of Gluster — multiple copies of the data, and automatic failover if
something goes wrong. To set up a replicated volume:

::

        gluster volume create gv0 replica 2 node01.mydomain.net:/export/sdb1/brick node02.mydomain.net:/export/sdb1/brick

Breaking this down into pieces, the first part says to create a gluster
volume named gv0 (the name is arbitrary, gv0 was chosen simply because
it’s less typing than gluster\_volume\_0). Next, we tell it to make the
volume a replica volume, and to keep a copy of the data on at least 2
bricks at any given time. Since we only have two bricks total, this
means each server will house a copy of the data. Lastly, we specify
which nodes to use, and which bricks on those nodes. The order here is
important when you have more bricks…it is possible (as of the most
current release as of this writing, Gluster 3.3) to specify the bricks
in a such a way that you would make both copies of the data reside on a
single node. This would make for an embarrassing explanation to your
boss when your bulletproof, completely redundant, always on super
cluster comes to a grinding halt when a single point of failure occurs.

Now, we can check to make sure things are working as expected:

::

        gluster volume info

And you should see results similar to the following:

::

        Volume Name: gv0
        Type: Replicate
        Volume ID: 8bc3e96b-a1b6-457d-8f7a-a91d1d4dc019
        Status: Created
        Number of Bricks: 1 x 2 = 2
        Transport-type: tcp
        Bricks:
        Brick1: node01.yourdomain.net:/export/sdb1/brick
        Brick2: node02.yourdomain.net:/export/sdb1/brick

This shows us essentially what we just specified during the volume
creation. The one this to mention is the “Status”. A status of “Created”
means that the volume has been created, but hasn’t yet been started,
which would cause any attempt to mount the volume fail.

Now, we should start the volume.

::

        gluster volume start gv0

Find all documentation `here <../index.md>`__