openstack/openstack-manuals
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openstack-manuals/doc/admin-guide-cloud/source/shared_file_systems_scheduling.rst
Jane Zadorozhna 61c744c2c5 Cloud Admin Guide: Shared File Systems updated information 
After the technical review the Shared File Systems service
documentation in the Cloud Admin Guide needs to be updated.

Read and fixed some typos and incorrect English constructions in
the sentences of all sections. Fixed indentations in code, tip
and note directives. Also updated the following info:
* Removed references to the Generic driver, because it is default
  only on Devstack. And even for Devstack the default driver is going
  to be changed.
* Divided 'Create share' subsection on 3 subsections: added general
  concepts and info of creating a share in 2 back end modes.
* Added info that with StandaloneNetworkPlugin the Shared File Systems
  service can be configured without Networking and Compute services.
* Added export paths for GlusterFS and HDFS.
* Added notes what driver in what mode you use in examples and a noted
  what modes exist and can be configured.
* Added a console sample for "manila rate-limits" command and described
  how to add API rate limits.
* Removed information and samples about a quota classes because they are
  not used in the Shared File Systems service and are not working
  properly for the current moment (in Liberty release).
* Added second purpose of the share types.
* Removed '/etc/manila/' in manila.conf file, because its path can be
  customly changed.
* Said that consistency groups is the experimental part of API starting
  with Liberty release.
* Updated a sample in shared_file_systems_multi_backend.html file.
* Removed 'Storage' from the Shared File Systems service official name
  according to [1] document.

[1] http://git.openstack.org/cgit/openstack/governance/tree/reference/projects.yaml

Change-Id: I0530ea3c6bf74311e271cdabca26cd10afcddc92
Closes-Bug: #1508457
2015-10-27 09:43:46 +00:00

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Scheduling

The Shared File Systems service provides unified access for variety of different types of shared file systems. To achieve this, the Shared File Systems service uses a scheduler. The scheduler collects information from active share services and takes decisions, what share service will be used to create a new share. To manage this process, the Shared File Systems service provides Share types API.

A share type is a list from key-value pairs called extra-specs. Some of them, called required and un-scoped extra-specs, scheduler uses for lookup the share service suitable for new share with specified share type. For more information about extra-specs and their type, see Capabilities and Extra-Specs <http://docs.openstack.org/developer/manila/devref/capabilities_and_extra_spec s.html> section in developer documentation.

The general scheduler workflow in described below.

  1. Share services report information about number of existing pools, their capacities and capabilities.
  2. When request on share creation comes in, scheduler picks a service and pool that fits the need best to serve the request, using share type filters and back end capabilities. If back end capabilities passes thought all filters request to the selected back end where the target pool resides.
  3. Share driver gets the message and lets the target pool serve the request as scheduler instructed. The scoped and un-scoped share type extra-specs are available for the driver implementation to use as needed.