.. _raid:

==================
RAID Configuration
==================

Overview
========
Ironic supports RAID configuration for bare metal nodes.  It allows operators
to specify the desired RAID configuration via the OpenStackClient CLI or REST
API.  The desired RAID configuration is applied on the bare metal during manual
cleaning.

The examples described here use the OpenStackClient CLI; please see the
`REST API reference <https://docs.openstack.org/api-ref/baremetal/>`_
for their corresponding REST API requests.

Prerequisites
=============
The bare metal node needs to use a hardware type that supports RAID
configuration. RAID interfaces may implement RAID configuration either in-band
or out-of-band. Software RAID is supported on all hardware, although with some
caveats - see `Software RAID`_ for details.

In-band RAID configuration (including software RAID) is done using the
Ironic Python Agent ramdisk. For in-band hardware RAID configuration,
a hardware manager which supports RAID should be bundled with the ramdisk.

Whether a node supports RAID configuration could be found using the CLI
command ``openstack baremetal node validate <node-uuid>``. In-band RAID is
usually implemented by the ``agent`` RAID interface.

Build agent ramdisk which supports RAID configuration
=====================================================

For doing in-band hardware RAID configuration, Ironic needs an agent ramdisk
bundled with a hardware manager which supports RAID configuration for your
hardware. For example, the :ref:`DIB_raid_support` should be used for HPE
Proliant Servers.

.. note::
    For in-band software RAID, the agent ramdisk does not need to be bundled
    with a hardware manager as the generic hardware manager in the Ironic
    Python Agent already provides (basic) support for software RAID.

RAID configuration JSON format
==============================
The desired RAID configuration and current RAID configuration are represented
in JSON format.

Target RAID configuration
-------------------------
This is the desired RAID configuration on the bare metal node.  Using the
OpenStackClient CLI (or REST API), the operator sets ``target_raid_config``
field of the node. The target RAID configuration will be applied during manual
cleaning.

Target RAID configuration is a dictionary having ``logical_disks``
as the key. The value for the ``logical_disks`` is a list of JSON
dictionaries. It looks like::

  {
    "logical_disks": [
      {<desired properties of logical disk 1>},
      {<desired properties of logical disk 2>},
      ...
    ]
  }

If the ``target_raid_config`` is an empty dictionary, it unsets the value of
``target_raid_config`` if the value was set with previous RAID configuration
done on the node.

Each dictionary of logical disk contains the desired properties of logical
disk supported by the hardware type. These properties are discoverable by::

    openstack baremetal driver raid property list <driver name>

Mandatory properties
^^^^^^^^^^^^^^^^^^^^

These properties must be specified for each logical
disk and have no default values:

- ``size_gb`` - Size (Integer) of the logical disk to be created in GiB.
  ``MAX`` may be specified if the logical disk should use all of the
  remaining space available. This can be used only when backing physical
  disks are specified (see below).

- ``raid_level`` - RAID level for the logical disk. Ironic supports the
  following RAID levels: 0, 1, 2, 5, 6, 1+0, 5+0, 6+0.

Optional properties
^^^^^^^^^^^^^^^^^^^

These properties have default values and they may be overridden in the
specification of any logical disk.

- ``volume_name`` - Name of the volume. Should be unique within the Node.
  If not specified, volume name will be auto-generated.

- ``is_root_volume`` - Set to ``true`` if this is the root volume. At
  most one logical disk can have this set to ``true``; the other
  logical disks must have this set to ``false``. The
  ``root device hint`` will be saved, if the RAID interface is capable of
  retrieving it. This is ``false`` by default.

Backing physical disk hints
^^^^^^^^^^^^^^^^^^^^^^^^^^^

These hints are specified for each logical disk to let Ironic find the desired
disks for RAID configuration. This is machine-independent information. This
serves the use-case where the operator doesn't want to provide individual
details for each bare metal node.

- ``share_physical_disks`` - Set to ``true`` if this logical disk can
  share physical disks with other logical disks. The default value is
  ``false``.

- ``disk_type`` - ``hdd`` or ``ssd``. If this is not specified, disk type
  will not be a criterion to find backing physical disks.

- ``interface_type`` - ``sata`` or ``scsi`` or ``sas``. If this is not
  specified, interface type will not be a criterion to
  find backing physical disks.

- ``number_of_physical_disks`` - Integer, number of disks to use for the
  logical disk. Defaults to minimum number of disks required for the
  particular RAID level.

Backing physical disks
^^^^^^^^^^^^^^^^^^^^^^

These are the actual machine-dependent information. This is suitable for
environments where the operator wants to automate the selection of physical
disks with a 3rd-party tool based on a wider range of attributes
(eg. S.M.A.R.T. status, physical location).  The values for these properties
are hardware dependent.

- ``controller`` - The name of the controller as read by the RAID interface.
  In order to trigger the setup of a Software RAID via the Ironic Python
  Agent, the value of this property needs to be set to ``software``.
- ``physical_disks`` - A list of physical disks to use as read by the
  RAID interface.

.. note::
    If properties from both "Backing physical disk hints" or
    "Backing physical disks" are specified, they should be consistent with
    each other.  If they are not consistent, then the RAID configuration
    will fail (because the appropriate backing physical disks could
    not be found).

.. _raid-config-examples:

Examples for ``target_raid_config``
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

*Example 1*. Single RAID disk of RAID level 5 with all of the space
available. Make this the root volume to which Ironic deploys the image:

.. code-block:: json

  {
    "logical_disks": [
      {
        "size_gb": "MAX",
        "raid_level": "5",
        "is_root_volume": true
      }
    ]
  }

*Example 2*. Two RAID disks. One with RAID level 5 of 100 GiB and make it
root volume and use SSD.  Another with RAID level 1 of 500 GiB and use
HDD:

.. code-block:: json

  {
    "logical_disks": [
      {
        "size_gb": 100,
        "raid_level": "5",
        "is_root_volume": true,
        "disk_type": "ssd"
      },
      {
        "size_gb": 500,
        "raid_level": "1",
        "disk_type": "hdd"
      }
    ]
  }

*Example 3*. Single RAID disk. I know which disks and controller to use:

.. code-block:: json

  {
    "logical_disks": [
      {
        "size_gb": 100,
        "raid_level": "5",
        "controller": "Smart Array P822 in Slot 3",
        "physical_disks": ["6I:1:5", "6I:1:6", "6I:1:7"],
        "is_root_volume": true
      }
    ]
  }

*Example 4*. Using backing physical disks:

.. code-block:: json

  {
    "logical_disks": [
      {
        "size_gb": 50,
        "raid_level": "1+0",
        "controller": "RAID.Integrated.1-1",
        "volume_name": "root_volume",
        "is_root_volume": true,
        "physical_disks": [
          "Disk.Bay.0:Encl.Int.0-1:RAID.Integrated.1-1",
          "Disk.Bay.1:Encl.Int.0-1:RAID.Integrated.1-1"
        ]
      },
      {
        "size_gb": 100,
        "raid_level": "5",
        "controller": "RAID.Integrated.1-1",
        "volume_name": "data_volume",
        "physical_disks": [
          "Disk.Bay.2:Encl.Int.0-1:RAID.Integrated.1-1",
          "Disk.Bay.3:Encl.Int.0-1:RAID.Integrated.1-1",
          "Disk.Bay.4:Encl.Int.0-1:RAID.Integrated.1-1"
        ]
      }
    ]
  }

*Example 5*. Software RAID with two RAID devices:

.. code-block:: json

  {
    "logical_disks": [
      {
        "size_gb": 100,
        "raid_level": "1",
        "controller": "software"
      },
      {
        "size_gb": "MAX",
        "raid_level": "0",
        "controller": "software"
      }
    ]
  }

Current RAID configuration
--------------------------
After target RAID configuration is applied on the bare metal node, Ironic
populates the current RAID configuration.  This is populated in the
``raid_config`` field in the Ironic node. This contains the details about
every logical disk after they were created on the bare metal node. It
contains details like RAID controller used, the backing physical disks used,
WWN of each logical disk, etc. It also contains information about each
physical disk found on the bare metal node.

To get the current RAID configuration::

    openstack baremetal node show <node-uuid-or-name>

Workflow
========

* Operator configures the bare metal node with a hardware type that has
  a ``RAIDInterface`` other than ``no-raid``. For instance, for Software RAID,
  this would be ``agent``.

* For in-band RAID configuration, operator builds an agent ramdisk which
  supports RAID configuration by bundling the hardware manager with the
  ramdisk. See `Build agent ramdisk which supports RAID configuration`_ for
  more information.

* Operator prepares the desired target RAID configuration as mentioned in
  `Target RAID configuration`_. The target RAID configuration is set on
  the Ironic node::

      openstack baremetal node set <node-uuid-or-name> \
         --target-raid-config <JSON file containing target RAID configuration>

  The CLI command can accept the input from standard input also::

       openstack baremetal node set <node-uuid-or-name> \
          --target-raid-config -

* Create a JSON file with the RAID clean steps for manual cleaning. Add other
  clean steps as desired::

    [{
      "interface": "raid",
      "step": "delete_configuration"
    },
    {
      "interface": "raid",
      "step": "create_configuration"
    }]

  .. note::
    'create_configuration' doesn't remove existing disks.  It is recommended
    to add 'delete_configuration' before 'create_configuration' to make
    sure that only the desired logical disks exist in the system after
    manual cleaning.

* Bring the node to ``manageable`` state and do a ``clean`` action to start
  cleaning on the node::

      openstack baremetal node clean <node-uuid-or-name> \
         --clean-steps <JSON file containing clean steps created above>

* After manual cleaning is complete, the current RAID configuration is
  reported in the ``raid_config`` field when running::

      openstack baremetal node show <node-uuid-or-name>

Software RAID
=============

Building Linux software RAID in-band (via the Ironic Python Agent ramdisk)
is supported starting with the Train release. It is requested by using the
``agent`` RAID interface and RAID configuration with all controllers set
to ``software``. You can find a software RAID configuration example in
:ref:`raid-config-examples`.

There are certain limitations to be aware of:

* Only the mandatory properties (plus the required ``controller`` property)
  from `Target RAID configuration`_ are currently supported.

* There is no way to select the disks which are used to set up the software
  RAID, so the Ironic Python Agent will use all available disks. This seems
  appropriate for servers with 2 or 4 disks, but needs to be considered when
  disk arrays are attached.

* The number of created Software RAID devices must be 1 or 2. If there is only
  one Software RAID device, it has to be a RAID-1. If there are two, the first
  one has to be a RAID-1, while the RAID level for the second one can
  0, 1, or 1+0. As the first RAID device will be the deployment device,
  enforcing a RAID-1 reduces the risk of ending up with a non-booting node
  in case of a disk failure.

* Building RAID will fail if the target disks are already partitioned. Wipe the
  disks using e.g. the ``erase_devices_metadata`` clean step before building
  RAID::

    [{
      "interface": "raid",
      "step": "delete_configuration"
    },
    {
      "interface": "deploy",
      "step": "erase_devices_metadata"
    {
      "interface": "raid",
      "step": "create_configuration"
    }]

* If local boot is going to be used, the final instance image must have the
  ``mdadm`` utility installed and needs to be able to detect software RAID
  devices at boot time (which is usually done by having the RAID drivers
  embedded in the image's initrd).

* Regular cleaning will not remove RAID configuration (similarly to hardware
  RAID). To destroy RAID run the ``delete_configuration`` manual clean step.

* There is no support for partition images, only whole-disk images are
  supported with Software RAID. See :doc:`/install/configure-glance-images`.

Using RAID in nova flavor for scheduling
========================================

The operator can specify the `raid_level` capability in nova flavor for node to be selected
for scheduling::

  openstack flavor set my-baremetal-flavor --property capabilities:raid_level="1+0"

Developer documentation
=======================
In-band RAID configuration is done using IPA ramdisk. IPA ramdisk has
support for pluggable hardware managers which can be used to extend the
functionality offered by IPA ramdisk using stevedore plugins.  For more
information, see Ironic Python Agent `Hardware Manager`_ documentation.

.. _`Hardware Manager`: https://docs.openstack.org/ironic-python-agent/latest/install/index.html#hardware-managers

The hardware manager that supports RAID configuration should do the following:

#. Implement a method named ``create_configuration``. This method creates
   the RAID configuration as given in ``target_raid_config``. After successful
   RAID configuration, it returns the current RAID configuration information
   which ironic uses to set ``node.raid_config``.

#. Implement a method named ``delete_configuration``. This method deletes
   all the RAID disks on the bare metal.

#. Return these two clean steps in ``get_clean_steps`` method with priority
   as 0. Example::

        return [{'step': 'create_configuration',
                 'interface': 'raid',
                 'priority': 0},
                {'step': 'delete_configuration',
                 'interface': 'raid',
                 'priority': 0}]

