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ironic
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Update software RAID configuration documentation 

This provides a bunch of updates based on user testing of the feature.
Also the lines are wrapped and inter-document links are created.

Change-Id: Ia3408aee3ebcd4ad5deedaa48967f46134ad2cfc
This commit is contained in:
Dmitry Tantsur 2019-08-01 14:43:06 +02:00
parent af61985d03
commit 521c086853
1 changed files with 45 additions and 24 deletions
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69
doc/source/admin/raid.rst
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@ -19,13 +19,16 @@ 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.
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.
In-band RAID configuration is done using the Ironic Python Agent
ramdisk. For in-band RAID configuration using agent ramdisk, 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>``.
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
=====================================================
@ -151,10 +154,7 @@ The RAID properties can be split into 4 different types:
will fail (because the appropriate backing physical disks could
not be found).
.. note::
For software RAID as provided by the generic hardware manager that ships
with the Ironic Python Agent, only the mandatory properties (plus the
required ``controller`` property) are currently supported.
.. _raid-config-examples:
Examples for ``target_raid_config``
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -320,25 +320,46 @@ Workflow
openstack baremetal node show <node-uuid-or-name>
Limitations of Software RAID
============================
Software RAID
=============
There are certain limitations to be aware of when setting up a Software RAID via the
Ironic Python Agent:
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 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.
There are certain limitations to be aware of:
* 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.
* Only the mandatory properties (plus the required ``controller`` property)
from `Target RAID configuration`_ are currently supported.
* There is no support for partition images, only whole-disk images are supported with
Software RAID.
* 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_device_metadata`` clean step before building
RAID.
* 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
========================================