openstack/openstack-manuals
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Merge "Correct host aggregate and availability zone info"

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Jenkins 2015-05-25 07:06:18 +00:00 committed by Gerrit Code Review
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doc/common/section_cli_nova_host_aggregates.xml
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@ -8,18 +8,31 @@
xmlns:xlink="http://www.w3.org/1999/xlink"
version="5.0"
xml:id="host-aggregates">
<title>Host aggregates</title>
<para>Host aggregates are a mechanism to further partition an
availability zone; while availability zones are visible to
users, host aggregates are only visible to administrators.
Host Aggregates provide a mechanism to allow administrators to
assign key-value pairs to groups of machines. Each node can
have multiple aggregates, each aggregate can have multiple
key-value pairs, and the same key-value pair can be assigned
to multiple aggregates. This information can be used in the
scheduler to enable advanced scheduling, to set up hypervisor
resource pools or to define logical groups for
migration.</para>
<title>Host aggregates and availability zones</title>
<para>
Host aggregates are a mechanism for partitioning hosts in an OpenStack
cloud, or a region of an OpenStack cloud, based on arbitrary
characteristics. Examples where an administrator may want to do this
include where a group of hosts have additional hardware or performance
characteristics.
</para>
<para>
Host aggregates are not explicitly exposed to users.
Instead administrators map flavors to host aggregates. Administrators
do this by setting metadata on a host aggregate, and matching flavor
extra specifications. The scheduler then endeavors to match user
requests for instance of the given flavor to a host aggregate with the
same key-value pair in its metadata. Compute nodes can be in more than
one host aggregate.
</para>
<para>
Administrators are able to optionally expose a host aggregate as an
availability zone. Availability zones are different to host aggregates
in that they are explicitly exposed to the user, and hosts can only be
in a single availability zone. Administrators can configure a default
availability zone where instances will be scheduled when the user
fails to specify one.
</para>
<simplesect>
<title>Command-line interface</title>
<para>The <command>nova</command> command-line tool supports
@ -34,19 +47,18 @@
<varlistentry>
<term><command>nova aggregate-create
<replaceable>&lt;name></replaceable>
<replaceable>&lt;availability-zone></replaceable></command></term>
<replaceable>[availability-zone]</replaceable></command></term>
<listitem>
<para>Create a new aggregate named
<replaceable>&lt;name></replaceable>
in availability zone
<replaceable>&lt;availability-zone></replaceable>.
Returns the ID of the newly created
aggregate. Hosts can be made available to
multiple availability zones, but
administrators should be careful when
adding the host to a different host
aggregate within the same availability
zone and pay attention when using the
<replaceable>&lt;name></replaceable>, and
optionally in availability zone
<replaceable>[availability-zone]</replaceable>
if specified. The command returns the ID of the
newly created aggregate. Hosts can be made
available to multiple host aggregates. Be careful
when adding a host to an additional host
aggregate when the host is also in an availability
zone. Pay attention when using the
<command>aggregate-set-metadata</command>
and <command>aggregate-update</command>
commands to avoid user confusion when they