e3f26b3f11
- swift, swift-init, swift-recon, swift-ring-builder Change-Id: I7838d379fb77adf2f17acd5d920cb33dde6450a6 Partial-bug: 1238668
116 lines
4.4 KiB
XML
116 lines
4.4 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE section [
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<!ENTITY % openstack SYSTEM "entities/openstack.ent">
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%openstack;
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]>
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<section xmlns="http://docbook.org/ns/docbook"
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xmlns:xi="http://www.w3.org/2001/XInclude"
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xmlns:xlink="http://www.w3.org/1999/xlink"
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version="5.0"
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xml:id="storage-concepts">
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<title>Storage concepts</title>
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<para>The OpenStack stack uses the following storage types:</para>
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<table rules="all">
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<caption>Storage types</caption>
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<col width="33%"/>
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<col width="33%"/>
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<col width="33%"/>
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<thead>
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<tr>
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<td>On-instance / ephemeral</td>
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<td>Block storage (cinder)</td>
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<td>Object Storage (swift)</td>
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</tr>
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</thead>
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<tbody>
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<tr>
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<td>Runs operating systems and provides scratch space</td>
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<td>Used for adding additional persistent storage to a virtual
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machine (VM)</td>
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<td>Used for storing virtual machine images and data</td>
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</tr>
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<tr>
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<td>Persists until VM is terminated</td>
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<td>Persists until deleted</td>
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<td>Persists until deleted</td>
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</tr>
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<tr>
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<td>Access associated with a VM</td>
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<td>Access associated with a VM</td>
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<td>Available from anywhere</td>
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</tr>
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<tr>
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<td>Implemented as a filesystem underlying OpenStack
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Compute</td>
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<td>Mounted via OpenStack Block Storage controlled protocol
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(for example, iSCSI)</td>
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<td>REST API</td>
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</tr>
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<tr>
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<td>Administrator configures size setting, based on
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flavors</td>
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<td>Sizings based on need</td>
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<td>Easily scalable for future growth</td>
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</tr>
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<tr>
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<td>Example: 10 GB first disk, 30 GB/core second disk</td>
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<td>Example: 1 TB "extra hard drive"</td>
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<td>Example: 10s of TBs of data set storage</td>
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</tr>
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</tbody>
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</table>
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<para>You should note that:<itemizedlist>
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<listitem>
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<para><emphasis>You cannot use OpenStack Object Storage like a
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traditional hard drive.</emphasis> The Object Storage relaxes some
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of the constraints of a POSIX-style file system to get other gains.
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You can access the objects through an API which uses HTTP.
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Subsequently you don't have to provide atomic operations (that is,
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relying on eventual consistency), you can scale a storage system
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easily and avoid a central point of failure.</para>
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</listitem>
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<listitem>
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<para><emphasis>The OpenStack Image Service is used to manage
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the virtual machine images in an OpenStack cluster, not
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store them.</emphasis> It provides an abstraction to different
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methods for storage - a bridge to the storage, not the storage
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itself.</para>
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</listitem>
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<listitem>
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<para><emphasis>The OpenStack Object Storage can function on its
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own.</emphasis> The Object Storage (swift) product can be
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used independently of the Compute (nova) product.</para>
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</listitem>
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</itemizedlist>
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</para>
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<variablelist>
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<title>Command-line clients and other interfaces</title>
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<varlistentry>
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<term>swift client</term>
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<listitem>
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<para>Enables users to submit commands to the REST API through
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a command-line client authorized as either a admin user,
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reseller user, or swift user.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term>swift-init</term>
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<listitem><para>Script that initializes the building of the ring
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file, takes daemon names as parameter and offers commands.
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Documented in
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<link xlink:href="http://docs.openstack.org/developer/swift/admin_guide.html#managing-services">http://docs.openstack.org/developer/swift/admin_guide.html#managing-services</link>.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term>swift-recon</term>
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<listitem><para></para></listitem>
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</varlistentry>
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<varlistentry>
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<term>swift-ring-builder</term>
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<listitem><para>Storage ring build and rebalance utility.
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Documented in <link
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xlink:href="http://docs.openstack.org/developer/swift/admin_guide.html#managing-the-rings">http://docs.openstack.org/developer/swift/admin_guide.html#managing-the-rings</link>.</para></listitem>
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</varlistentry>
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</variablelist>
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</section>
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