openstack/nova
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Merge "Docs: update the concept guide for Host topics"

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Jenkins 2015-12-03 16:55:09 +00:00 committed by Gerrit Code Review
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api-guide/source/general_info.rst
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@ -115,7 +115,7 @@ In this section we focus on this related to networking.
Administrator Concepts Administrator Concepts
======================= =======================
Come APIs are largely focused on administration of Nova, and generally focus Some APIs are largely focused on administration of Nova, and generally focus
on compute hosts rather than servers. on compute hosts rather than servers.
- **Services** - **Services**
@ -196,11 +196,31 @@ on compute hosts rather than servers.
- **Hosts** - **Hosts**
TODO Hosts are the *physical machines* that provide the resources for the virtual
servers created in Nova. They run a ``hypervisor`` (see definition below)
that handles the actual creation and management of the virtual servers.
Hosts also run the ``Nova compute service``, which receives requests from
Nova to interact with the virtual servers on that machine. When compute
service receives a request, it calls the appropriate methods of the driver
for that hypervisor in order to carry out the request. The driver acts as
the translator from generic Nova requests to hypervisor-specific calls.
Hosts report their current state back to Nova, where it is tracked by the
scheduler service, so that the scheduler can place requests for new virtual
servers on the hosts that can best fit them.
- **Host Actions** - **Host Actions**
TODO A *host action* is one that affects the physical host machine, as opposed to
actions that only affect the virtual servers running on that machine. There
are three 'power' actions that are supported: *startup*, *shutdown*, and
*reboot*. There are also two 'state' actions: enabling/disabling the host,
and setting the host into or out of maintenance mode. Of course, carrying
out these actions can affect running virtual servers on that host, so their
state will need to be considered before carrying out the host action. For
example, if you want to call the 'shutdown' action to turn off a host
machine, you might want to migrate any virtual servers on that host before
shutting down the host machine so that the virtual servers continue to be
available without interruption.
- **Hypervisors** - **Hypervisors**