openstack-manuals/doc/admin-guide-cloud/source/blockstorage_volume_number_weigher.rst

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.. _volume_number_weigher:
.. highlight: ini
:linenothreshold: 5
=======================================
Configure and use volume number weigher
=======================================
OpenStack Block Storage enables you to choose a volume back end according
to ``free_capacity`` and ``allocated_capacity``. The volume number weigher
feature lets the scheduler choose a volume back end based on its volume
number in the volume back end. This can provide another means to improve
the volume back ends' I/O balance and the volumes' I/O performance.
Enable volume number weigher
~~~~~~~~~~~~~~~~~~~~~~~~~~~~
To enable a volume number weigher, set the
``scheduler_default_weighers`` to ``VolumeNumberWeigher`` flag in the
:file:`cinder.conf` file to define ``VolumeNumberWeigher``
as the selected weigher.
Configure multiple-storage back ends
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
To configure ``VolumeNumberWeigher``, use ``LVMVolumeDriver``
as the volume driver.
This configuration defines two LVM volume groups: ``stack-volumes`` with
10 GB capacity and ``stack-volumes-1`` with 60 GB capacity.
This example configuration defines two back ends:
.. code-block:: ini
:linenos:
scheduler_default_weighers=VolumeNumberWeigher
enabled_backends=lvmdriver-1,lvmdriver-2
[lvmdriver-1]
volume_group=stack-volumes
volume_driver=cinder.volume.drivers.lvm.LVMVolumeDriver
volume_backend_name=LVM
[lvmdriver-2]
volume_group=stack-volumes-1
volume_driver=cinder.volume.drivers.lvm.LVMVolumeDriver
volume_backend_name=LVM
Volume type
~~~~~~~~~~~
Define a volume type in Block Storage::
$ cinder type-create lvm
Create an extra specification that links the volume type to a back-end name::
$ cinder type-key lvm set volume_backend_name=LVM
This example creates a lvm volume type with
``volume_backend_name=LVM`` as extra specifications.
Usage
~~~~~
To create six 1-GB volumes, run the
:command:`cinder create --volume-type lvm 1` command six times::
$ cinder create --volume-type lvm 1
This command creates three volumes in ``stack-volumes`` and
three volumes in ``stack-volumes-1``.
List the available volumes::
# lvs
LV VG Attr LSize Pool Origin Data% Move Log Copy% Convert
volume-3814f055-5294-4796-b5e6-1b7816806e5d stack-volumes -wi-a---- 1.00g
volume-72cf5e79-99d2-4d23-b84e-1c35d3a293be stack-volumes -wi-a---- 1.00g
volume-96832554-0273-4e9d-902b-ad421dfb39d1 stack-volumes -wi-a---- 1.00g
volume-169386ef-3d3e-4a90-8439-58ceb46889d9 stack-volumes-1 -wi-a---- 1.00g
volume-460b0bbb-d8a0-4bc3-9882-a129a5fe8652 stack-volumes-1 -wi-a---- 1.00g
volume-9a08413b-0dbc-47c9-afb8-41032ab05a41 stack-volumes-1 -wi-a---- 1.00g