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50 lines
3.0 KiB
XML
50 lines
3.0 KiB
XML
<?xml version='1.0' encoding='utf-8' ?>
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<!DOCTYPE section PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<!ENTITY % BOOK_ENTITIES SYSTEM "cloudstack.ent">
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%BOOK_ENTITIES;
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]>
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<!-- Licensed to the Apache Software Foundation (ASF) under one
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or more contributor license agreements. See the NOTICE file
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distributed with this work for additional information
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regarding copyright ownership. The ASF licenses this file
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to you under the Apache License, Version 2.0 (the
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"License"); you may not use this file except in compliance
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with the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing,
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software distributed under the License is distributed on an
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"AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
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KIND, either express or implied. See the License for the
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specific language governing permissions and limitations
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under the License.
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-->
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<section id="about-regions">
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<title>About Regions</title>
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<para>To increase reliability of the cloud, you can optionally group resources into multiple geographic regions.
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A region is the largest available organizational unit within a &PRODUCT; deployment.
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A region is made up of several availability zones, where each zone is roughly equivalent to a datacenter.
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Each region is controlled by its own cluster of Management Servers, running in one of the zones.
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The zones in a region are typically located in close geographical proximity.
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Regions are a useful technique for providing fault tolerance and disaster recovery.</para>
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<para>By grouping zones into regions, the cloud can achieve higher availability and scalability.
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User accounts can span regions, so that users can deploy VMs in multiple, widely-dispersed regions.
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Even if one of the regions becomes unavailable, the services are still available to the end-user through VMs deployed in another region.
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And by grouping communities of zones under their own nearby Management Servers, the latency of communications within the cloud is reduced
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compared to managing widely-dispersed zones from a single central Management Server.
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</para>
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<para>
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Usage records can also be consolidated and tracked at the region level, creating reports or invoices for each geographic region.
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</para>
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<mediaobject>
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<imageobject>
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<imagedata fileref="./images/region-overview.png" />
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</imageobject>
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<textobject><phrase>region-overview.png: Nested structure of a region.</phrase></textobject>
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</mediaobject>
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<para>Regions are visible to the end user. When a user starts a guest VM on a particular &PRODUCT; Management Server,
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the user is implicitly selecting that region for their guest.
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Users might also be required to copy their private templates to additional regions to enable creation of guest VMs using their templates in those regions.</para>
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</section> |