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nova
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Merge "Add docs for image type support request filter"

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Zuul 2019-05-15 22:18:52 +00:00 committed by Gerrit Code Review
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doc/source/admin/configuration/schedulers.rst
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@ -51,6 +51,32 @@ target host. For information about instance evacuation, see
.. _compute-scheduler-filters:
Prefiltering
~~~~~~~~~~~~
As of the Rocky release, the scheduling process includes a prefilter
step to increase the efficiency of subsequent stages. These prefilters
are largely optional, and serve to augment the request that is sent to
placement to reduce the set of candidate compute hosts based on
attributes that placement is able to answer for us ahead of time. In
addition to the prefilters listed here, also see `Tenant Isolation
with Placement`_ and `Availability Zones with Placement`_.
Compute Image Type Support
--------------------------
Starting in the Train release, there is a prefilter available for
excluding compute nodes that do not support the ``disk_format`` of the
image used in a boot request. This behavior is enabled by setting
:oslo.config:option:`[scheduler]/query_placement_for_image_type_support=True
<scheduler.query_placement_for_image_type_support>`. For
example, the libvirt driver, when using ceph as an ephemeral backend,
does not support ``qcow2`` images (without an expensive conversion
step). In this case (and especially if you have a mix of ceph and
non-ceph backed computes), enabling this feature will ensure that the
scheduler does not send requests to boot a ``qcow2`` image to computes
backed by ceph.
Filter scheduler
~~~~~~~~~~~~~~~~