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.. index:: RBD

Starting to use RBD

Introduction

RBD is the block device component of Ceph. It provides a block device interface to a Linux machine, while striping the data across multiple RADOS objects for improved performance. For more information, see :ref:`rbd`.

Installation

To use RBD, you need to install a Ceph cluster. Follow the instructions in :doc:`/ops/install/index`. Continue with these instructions once you have a healthy cluster running.

Setup

The default pool used by RBD is called rbd. It is created for you as part of the installation. If you wish to use multiple pools, for example for access control, see :ref:`create-new-pool`.

First, we need a client key that is authorized to access the right pool. Follow the instructions in :ref:`add-new-key`. Let's set the id of the key to be bar. You could set up one key per machine using RBD, or let them share a single key; your call. Make sure the keyring containing the new key is available on the machine.

Then, authorize the key to access the new pool. Follow the instructions in :ref:`auth-pool`.

Usage

RBD can be accessed in two ways:

  • as a block device on a Linux machine
  • via the rbd network storage driver in Qemu/KVM

Example: As a block device

Using the client.bar key you set up earlier, we can create an RBD image called tengigs:

rbd --name=client.bar create --size=10240 tengigs

And then make that visible as a block device:

touch secretfile
chmod go= secretfile
ceph-authtool --name=bar --print-key /etc/ceph/client.bar.keyring >secretfile
rbd map tengigs --user bar --secret secretfile

.. todo:: the secretfile part is really clumsy

For more information, see :doc:`rbd </man/8/rbd>`(8).

Example: As a Qemu/KVM storage driver via Libvirt

You'll need kvm v0.15, and libvirt v0.8.7 or newer.

Create the RBD image as above, and then refer to it in the libvirt virtual machine configuration:

<disk type='network' device='disk'>
  <source protocol='rbd' name='rbd/tengigs'>
      <host name='10.0.0.101' port='6789'/>
      <host name='10.0.0.102' port='6789'/>
      <host name='10.0.0.103' port='6789'/>
  </source>
  <target dev='vda' bus='virtio'/>
</disk

.. todo:: use secret keys


.. todo:: ceph.conf usage for mon addresses


.. todo:: pending libvirt xml schema changes