e08ae456c0
1.) Also deleted the commands that are explaining for different linux distros. 2.) And also replaced one TODO link Change-Id: I2557ff8bd93b21129b26a03c8c2b0b714949b9cf
186 lines
6.2 KiB
ReStructuredText
186 lines
6.2 KiB
ReStructuredText
.. _multi_backend:
|
|
|
|
====================================
|
|
Configure multiple-storage back ends
|
|
====================================
|
|
|
|
When you configure multiple-storage back ends, you can create several
|
|
back-end storage solutions that serve the same OpenStack Compute
|
|
configuration and one ``cinder-volume`` is launched for each back-end
|
|
storage or back-end storage pool.
|
|
|
|
In a multiple-storage back-end configuration, each back end has a name
|
|
(``volume_backend_name``). Several back ends can have the same name.
|
|
In that case, the scheduler properly decides which back end the volume
|
|
has to be created in.
|
|
|
|
The name of the back end is declared as an extra-specification of a
|
|
volume type (such as, ``volume_backend_name=LVM``). When a volume
|
|
is created, the scheduler chooses an appropriate back end to handle the
|
|
request, according to the volume type specified by the user.
|
|
|
|
Enable multiple-storage back ends
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
To enable a multiple-storage back ends, you must set the
|
|
`enabled_backends` flag in the ``cinder.conf`` file.
|
|
This flag defines the names (separated by a comma) of the configuration
|
|
groups for the different back ends: one name is associated to one
|
|
configuration group for a back end (such as, ``[lvmdriver-1]``).
|
|
|
|
.. note::
|
|
|
|
The configuration group name is not related to the ``volume_backend_name``.
|
|
|
|
.. note::
|
|
|
|
After setting the ``enabled_backends`` flag on an existing cinder
|
|
service, and restarting the Block Storage services, the original ``host``
|
|
service is replaced with a new host service. The new service appears
|
|
with a name like ``host@backend``. Use:
|
|
|
|
.. code-block:: console
|
|
|
|
$ cinder-manage volume update_host --currenthost CURRENTHOST --newhost CURRENTHOST@BACKEND
|
|
|
|
to convert current block devices to the new host name.
|
|
|
|
The options for a configuration group must be defined in the group
|
|
(or default options are used). All the standard Block Storage
|
|
configuration options (``volume_group``, ``volume_driver``, and so on)
|
|
might be used in a configuration group. Configuration values in
|
|
the ``[DEFAULT]`` configuration group are not used.
|
|
|
|
These examples show three back ends:
|
|
|
|
.. code-block:: ini
|
|
|
|
enabled_backends=lvmdriver-1,lvmdriver-2,lvmdriver-3
|
|
[lvmdriver-1]
|
|
volume_group=cinder-volumes-1
|
|
volume_driver=cinder.volume.drivers.lvm.LVMVolumeDriver
|
|
volume_backend_name=LVM
|
|
[lvmdriver-2]
|
|
volume_group=cinder-volumes-2
|
|
volume_driver=cinder.volume.drivers.lvm.LVMVolumeDriver
|
|
volume_backend_name=LVM
|
|
[lvmdriver-3]
|
|
volume_group=cinder-volumes-3
|
|
volume_driver=cinder.volume.drivers.lvm.LVMVolumeDriver
|
|
volume_backend_name=LVM_b
|
|
|
|
In this configuration, ``lvmdriver-1`` and ``lvmdriver-2`` have the same
|
|
``volume_backend_name``. If a volume creation requests the ``LVM``
|
|
back end name, the scheduler uses the capacity filter scheduler to choose
|
|
the most suitable driver, which is either ``lvmdriver-1`` or ``lvmdriver-2``.
|
|
The capacity filter scheduler is enabled by default. The next section
|
|
provides more information. In addition, this example presents a
|
|
``lvmdriver-3`` back end.
|
|
|
|
.. note::
|
|
|
|
For Fiber Channel drivers that support multipath, the configuration group
|
|
requires the ``use_multipath_for_image_xfer=true`` option. In
|
|
the example below, you can see details for HPE 3PAR and EMC Fiber
|
|
Channel drivers.
|
|
|
|
.. code-block:: ini
|
|
|
|
[3par]
|
|
use_multipath_for_image_xfer = true
|
|
volume_driver = cinder.volume.drivers.hpe.hpe_3par_fc.HPE3PARFCDriver
|
|
volume_backend_name = 3parfc
|
|
|
|
[emc]
|
|
use_multipath_for_image_xfer = true
|
|
volume_driver = cinder.volume.drivers.emc.emc_smis_fc.EMCSMISFCDriver
|
|
volume_backend_name = emcfc
|
|
|
|
Configure Block Storage scheduler multi back end
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
You must enable the `filter_scheduler` option to use
|
|
multiple-storage back ends. The filter scheduler:
|
|
|
|
#. Filters the available back ends. By default, ``AvailabilityZoneFilter``,
|
|
``CapacityFilter`` and ``CapabilitiesFilter`` are enabled.
|
|
|
|
#. Weights the previously filtered back ends. By default, the
|
|
`CapacityWeigher` option is enabled. When this option is
|
|
enabled, the filter scheduler assigns the highest weight to back
|
|
ends with the most available capacity.
|
|
|
|
The scheduler uses filters and weights to pick the best back end to
|
|
handle the request. The scheduler uses volume types to explicitly create
|
|
volumes on specific back ends. For more information about filter and weighing,
|
|
see :ref:`filter_weigh_scheduler`.
|
|
|
|
|
|
Volume type
|
|
~~~~~~~~~~~
|
|
|
|
Before using it, a volume type has to be declared to Block Storage.
|
|
This can be done by the following command:
|
|
|
|
.. code-block:: console
|
|
|
|
$ cinder --os-username admin --os-tenant-name admin type-create lvm
|
|
|
|
Then, an extra-specification has to be created to link the volume
|
|
type to a back end name. Run this command:
|
|
|
|
.. code-block:: console
|
|
|
|
$ cinder --os-username admin --os-tenant-name admin type-key lvm set \
|
|
volume_backend_name=LVM_iSCSI
|
|
|
|
This example creates a ``lvm`` volume type with
|
|
``volume_backend_name=LVM_iSCSI`` as extra-specifications.
|
|
|
|
Create another volume type:
|
|
|
|
.. code-block:: console
|
|
|
|
$ cinder --os-username admin --os-tenant-name admin type-create lvm_gold
|
|
|
|
$ cinder --os-username admin --os-tenant-name admin type-key lvm_gold set \
|
|
volume_backend_name=LVM_iSCSI_b
|
|
|
|
This second volume type is named ``lvm_gold`` and has ``LVM_iSCSI_b`` as
|
|
back end name.
|
|
|
|
.. note::
|
|
|
|
To list the extra-specifications, use this command:
|
|
|
|
.. code-block:: console
|
|
|
|
$ cinder --os-username admin --os-tenant-name admin extra-specs-list
|
|
|
|
.. note::
|
|
|
|
If a volume type points to a ``volume_backend_name`` that does not
|
|
exist in the Block Storage configuration, the ``filter_scheduler``
|
|
returns an error that it cannot find a valid host with the suitable
|
|
back end.
|
|
|
|
Usage
|
|
~~~~~
|
|
|
|
When you create a volume, you must specify the volume type.
|
|
The extra-specifications of the volume type are used to determine which
|
|
back end has to be used.
|
|
|
|
.. code-block:: console
|
|
|
|
$ cinder create --volume_type lvm --display_name test_multi_backend 1
|
|
|
|
Considering the ``cinder.conf`` described previously, the scheduler
|
|
creates this volume on ``lvmdriver-1`` or ``lvmdriver-2``.
|
|
|
|
.. code-block:: console
|
|
|
|
$ cinder create --volume_type lvm_gold --display_name test_multi_backend 1
|
|
|
|
This second volume is created on ``lvmdriver-3``.
|