openstack/deb-sahara
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Merge "Docs updated with instance locality feature"

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Jenkins 2015-03-31 23:44:34 +00:00 committed by Gerrit Code Review
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doc/source/userdoc/features.rst
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@ -154,6 +154,44 @@ set ``enable_hypervisor_awareness`` option to ``True`` in Sahara configuration
file. In this case Sahara will add the compute node ID as a second level of
topology for Virtual Machines.
Volume-to-instance locality
---------------------------
Having an instance and an attached volume on the same physical host can be very
helpful in order to achieve high-performance disk I/O. To achieve this,
volume-to-instance locality should be used.
Cinder has ``InstanceLocalityFilter`` which enables selection of a storage
back-end located on the host where the instance's hypervisor is running. It
allows volumes to be created on the same physical host as the instance.
To enable this functionality for instances of a specific node group, the
``volume_local_to_instance`` field in node group template should be set to
``True`` and some extra configurations are needed:
* Cinder-volume service should be launched on every physical host and at least
one physical host should run both cinder-scheduler and cinder-volume services.
* ``InstanceLocalityFilter`` should be added to the list of default filters
(``scheduler_default_filters`` in Cinder config).
* The Extended Server Attributes extension needs to be active in Nova
(this is true by default), so that the ``OS-EXT-SRV-ATTR:host`` property is
returned when requesting instance info.
* The user making the call needs to have sufficient rights for the property to
be returned by Nova.
This can be made:
* by changing Nova's ``policy.json`` (the ``extended_server_attributes`` option)
* by setting an account with privileged rights in Cinder config:
.. sourcecode:: cfg
os_privileged_user_name =
os_privileged_user_password =
os_privileged_user_tenant =
It should be noted that in a situation when the host has no space for volume
creation, the created volume will have an ``Error`` state and can not be used.
Security group management
-------------------------