Synnefo » snf-ganeti » ganeti-local

- `RBD <http://ceph.newdream.net/>`_, kernel modules (rbd.ko/libceph.ko)

  and userspace utils (ceph-common)

packages, except for RBD, DRBD and Xen::

There are five disk templates you can choose from:

rbd

  The instance will use Volumes inside a RADOS cluster as backend for its

  disks. It will access them using the RADOS block device (RBD).

If the instance's disk template is of type rbd, then you can specify

the target node (which can be any node) explicitly, or specify an

iallocator plugin. If you omit both, the default iallocator will be

used to determine the target node::

  gnt-instance failover -n TARGET_NODE INSTANCE_NAME

If the instance's disk template is of type rbd, then you can specify

the target node (which can be any node) explicitly, or specify an

iallocator plugin. If you omit both, the default iallocator will be

used to determine the target node::

   gnt-instance migrate -n TARGET_NODE INSTANCE_NAME

7. If using RBD, run ``rbd unmap /dev/rbdN`` to unmap the RBD disks.

   Then remove the RBD disk images used by Ganeti, identified by their

   UUIDs (``rbd rm uuid.rbd.diskN``).

The node selection options in instance add and instance replace disks

If you choose to use RBD-based instances, there's no need for LVM

provisioning. However, this feature is experimental, and is not

recommended for production clusters.

Installing RBD

+++++++++++++++

Recommended on all nodes: RBD_ is required if you want to create

instances with RBD disks residing inside a RADOS cluster (make use of

the rbd disk template). RBD-based instances can failover or migrate to

any other node in the ganeti cluster, enabling you to exploit of all

Ganeti's high availabilily (HA) features.

.. attention::

   Be careful though: rbd is still experimental! For now it is

   recommended only for testing purposes.  No sensitive data should be

   stored there.

.. _RBD: http://ceph.newdream.net/

You will need the ``rbd`` and ``libceph`` kernel modules, the RBD/Ceph

userspace utils (ceph-common Debian package) and an appropriate

Ceph/RADOS configuration file on every VM-capable node.

You will also need a working RADOS Cluster accessible by the above

nodes.

RADOS Cluster

~~~~~~~~~~~~~

You will need a working RADOS Cluster accesible by all VM-capable nodes

to use the RBD template. For more information on setting up a RADOS

Cluster, refer to the `official docs <http://ceph.newdream.net/>`_.

If you want to use a pool for storing RBD disk images other than the

default (``rbd``), you should first create the pool in the RADOS

Cluster, and then set the corresponding rbd disk parameter named

``pool``.

Kernel Modules

~~~~~~~~~~~~~~

Unless your distribution already provides it, you might need to compile

the ``rbd`` and ``libceph`` modules from source. You will need Linux

Kernel 3.2 or above for the kernel modules. Alternatively you will have

to build them as external modules (from Linux Kernel source 3.2 or

above), if you want to run a less recent kernel, or your kernel doesn't

include them.

Userspace Utils

~~~~~~~~~~~~~~~

The RBD template has been tested with ``ceph-common`` v0.38 and

above. We recommend using the latest version of ``ceph-common``.

.. admonition:: Debian

   On Debian, you can just install the RBD/Ceph userspace utils with

   the following command::

      apt-get install ceph-common

Configuration file

~~~~~~~~~~~~~~~~~~

You should also provide an appropriate configuration file

(``ceph.conf``) in ``/etc/ceph``. For the rbd userspace utils, you'll

only need to specify the IP addresses of the RADOS Cluster monitors.

.. admonition:: ceph.conf

   Sample configuration file::

    [mon.a]

           host = example_monitor_host1

           mon addr = 1.2.3.4:6789

    [mon.b]

           host = example_monitor_host2

           mon addr = 1.2.3.5:6789

    [mon.c]

           host = example_monitor_host3

           mon addr = 1.2.3.6:6789

For more information, please see the `Ceph Docs

<http://ceph.newdream.net/docs/latest/>`_

List of parameters available for the **rbd** template:

pool

    The RADOS cluster pool, inside which all rbd volumes will reside.

    When a new RADOS cluster is deployed, the default pool to put rbd

    volumes (Images in RADOS terminology) is 'rbd'.

| {-t|--disk-template {diskless | file \| plain \| drbd \| rbd}}

rbd

    Disk devices will be rbd volumes residing inside a RADOS cluster.

plain, drbd or rbd disk template.

For instances with a drbd template, note that the disk grow operation

might complete on one node but fail on the other; this will leave the

instance with different-sized LVs on the two nodes, but this will not

create problems (except for unused space).

| **failover** [-f] [--ignore-consistency] [--ignore-ipolicy]

| [--shutdown-timeout=*N*]

| [{-n|--target-node} *node* \| {-I|--iallocator} *name*]

| [--submit]

| {*instance*}

mirrored templates (blockdev and rbd) (which can change to any other

If the instance's disk template is of type blockdev or rbd, then you

can explicitly specify the target node (which can be any node) using

the ``-n`` or ``--target-node`` option, or specify an iallocator plugin

using the ``-I`` or ``--iallocator`` option. If you omit both, the default

iallocator will be used to specify the target node.

[--no-runtime-changes]

[{-n|--target-node} *node* \| {-I|--iallocator} *name*] {*instance*}

Migrate will move the instance to its secondary node without shutdown.

As with failover, it only works for instances having the drbd disk

template or an externally mirrored disk template type such as blockdev

or rbd.

If the instance's disk template is of type blockdev or rbd, then you can

explicitly specify the target node (which can be any node) using the

``-n`` or ``--target-node`` option, or specify an iallocator plugin

using the ``-I`` or ``--iallocator`` option. If you omit both, the

default iallocator will be used to specify the target node.