Synnefo » snf-ganeti » ganeti-local

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  <!ENTITY dhdate      "<date>June 08, 2010</date>">

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  <!ENTITY dhsection   "<manvolnum>7</manvolnum>">

  <!ENTITY dhucpackage "<refentrytitle>ganeti</refentrytitle>">

  <!ENTITY dhpackage   "ganeti">

  <!ENTITY debian      "<productname>Debian</productname>">

  <!ENTITY gnu         "<acronym>GNU</acronym>">

  <!ENTITY gpl         "&gnu; <acronym>GPL</acronym>">

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]>

<refentry>

  <refentryinfo>

    <copyright>

      <year>2006</year>

      <year>2007</year>

      <year>2008</year>

      <year>2009</year>

      <year>2010</year>

      <holder>Google Inc.</holder>

    </copyright>

    &dhdate;

  </refentryinfo>

  <refmeta>

    &dhucpackage;

    &dhsection;

    <refmiscinfo>Ganeti 2.2</refmiscinfo>

  </refmeta>

  <refnamediv>

    <refname>&dhpackage;</refname>

    <refpurpose>cluster-based virtualization management</refpurpose>

  </refnamediv>

  <refsynopsisdiv>

    <screen>

# gnt-cluster init cluster1.example.com

# gnt-node add node2.example.com

# gnt-instance add -n node2.example.com \

> -o debootstrap --disk 0:size=30g \

> -t plain instance1.example.com

    </screen>

  </refsynopsisdiv>

  <refsect1>

    <title>DESCRIPTION</title>

    <para>

      The Ganeti software manages physical nodes and virtual instances

      of a cluster based on a virtualization software. The current

      version (2.2) supports Xen 3.x and KVM (72 or above) as hypervisors.

    </para>

  </refsect1>

  <refsect1>

    <title>Quick start</title>

    <para>

      First you must install the software on all the cluster nodes,

      either from sources or (if available) from a package. The next

      step is to create the initial cluster configuration, using

      <userinput>gnt-cluster init</userinput>.

    </para>

    <para>

      Then you can add other nodes, or start creating instances.

    </para>

  </refsect1>

  <refsect1>

    <title>Cluster architecture</title>

    <para>

      In Ganeti 2.0, the architecture of the cluster is a little more

      complicated than in 1.2. The cluster is coordinated by a master

      daemon (<citerefentry>

      <refentrytitle>ganeti-masterd</refentrytitle>

      <manvolnum>8</manvolnum> </citerefentry>), running on the master

      node. Each node runs (as before) a node daemon, and the master

      has the <acronym>RAPI</acronym> daemon running too.

    </para>

    <refsect2>

      <title>Node roles</title>

      <para>Each node can be in one of the following states:

        <variablelist>

          <varlistentry>

            <term>master</term>

            <listitem>

              <para>

                Only one node per cluster can be in this role, and

                this node is the one holding the authoritative copy of

                the cluster configuration and the one that can

                actually execute commands on the cluster and modify

                the cluster state. See more details under

                <emphasis>Cluster configuration</emphasis>.

              </para>

            </listitem>

          </varlistentry>

          <varlistentry>

            <term>master_candidate</term>

            <listitem>

              <para>The node receives the full cluster configuration

              (configuration file and jobs) and can become a master

              via the <command>gnt-cluster master-failover</command>

              command. Nodes that are not in this state cannot

              transition into the master role due to missing

              state.</para>

            </listitem>

          </varlistentry>

          <varlistentry>

            <term>regular</term>

            <listitem>

              <para>This the normal state of a node.</para>

            </listitem>

          </varlistentry>

          <varlistentry>

            <term>drained</term>

            <listitem>

              <para>Nodes in this state are functioning normally but

              cannot receive new instance, because the intention is to

              set them to <emphasis>offline</emphasis> or remove them

              from the cluster.</para>

            </listitem>

          </varlistentry>

          <varlistentry>

            <term>offline</term>

            <listitem>

              <para>These nodes are still recorded in the Ganeti

              configuration, but except for the master daemon startup

              voting procedure, they are not actually contacted by the

              master. This state was added in order to allow broken

              machines (that are being repaired) to remain in the

              cluster but without creating problems.</para>

            </listitem>

          </varlistentry>

        </variablelist>

      </para>

    </refsect2>

    <refsect2>

      <title>Node flags</title>

      <para>Nodes have two flags which govern which roles they can take:

        <variablelist>

          <varlistentry>

            <term>master_capable</term>

            <listitem>

              <para>

                The node can become a master candidate, and

                furthermore the master node. When this flag is

                disabled, the node cannot become a candidate; this can

                be useful for special networking cases, or less

                reliable hardware.

              </para>

            </listitem>

          </varlistentry>

          <varlistentry>

            <term>vm_capable</term>

            <listitem>

              <para>

                The node can host instances. When enabled (the default

                state), the node will participate in instance

                allocation, capacity calculation, etc. When disabled,

                the node will be skipped in many cluster checks and

                operations.

              </para>

            </listitem>

          </varlistentry>

        </variablelist>

      </para>

    </refsect2>

    <refsect2>

      <title>Cluster configuration</title>

      <para>The master node keeps and is responsible for the cluster

      configuration. On the filesystem, this is stored under the

      <filename

      class="directory">@LOCALSTATEDIR@/ganeti/lib</filename>

      directory, and if the master daemon is stopped it can be backed

      up normally.</para>

      <para>The master daemon will replicate the configuration

      database called <filename>config.data</filename> and the job

      files to all the nodes in the master candidate role. It will

      also distribute a copy of some configuration values via the

      <emphasis>ssconf</emphasis> files, which are stored in the same

      directory and start with <filename>ssconf_</filename> prefix, to

      all nodes.</para>

    </refsect2>

    <refsect2>

      <title>Jobs</title>

      <para>

        All cluster modification are done via jobs. A job consists of

        one or more opcodes, and the list of opcodes is processed

        serially. If an opcode fails, the entire job is failed and

        later opcodes are no longer processed. A job can be in one of

        the following states:

        <variablelist>

          <varlistentry>

            <term>queued</term>

            <listitem>

              <simpara>The job has been submitted but not yet

              processed by the master daemon.</simpara>

            </listitem>

          </varlistentry>

          <varlistentry>

            <term>waiting</term>

            <listitem>

              <simpara>The job is waiting for for locks before the

              first of its opcodes.</simpara>

            </listitem>

          </varlistentry>

          <varlistentry>

            <term>canceling</term>

            <listitem>

              <para>The job is waiting for locks, but is has been

              marked for cancellation. It will not transition to

              <emphasis>running</emphasis>, but to

              <emphasis>canceled</emphasis>.

              </para>

            </listitem>

          </varlistentry>

          <varlistentry>

            <term>running</term>

            <listitem>

              <simpara>The job is currently being executed.</simpara>

            </listitem>

          </varlistentry>

          <varlistentry>

            <term>canceled</term>

            <listitem>

              <para>The job has been canceled before starting

              execution.</para>

            </listitem>

          </varlistentry>

          <varlistentry>

            <term>success</term>

            <listitem>

              <para>The job has finished successfully.</para>

            </listitem>

          </varlistentry>

          <varlistentry>

            <term>error</term>

            <listitem>

              <para>The job has failed during runtime, or the master

              daemon has been stopped during the job execution.</para>

            </listitem>

          </varlistentry>

        </variablelist>

      </para>

    </refsect2>

  </refsect1>

  <refsect1>

    <title>Common options</title>

    <para>

      Many Ganeti commands provide the following options. The availability for

      a certain command can be checked by calling the command using the

      <option>--help</option> option.

    </para>

    <cmdsynopsis>

      <command>gnt-<replaceable>...</replaceable> <replaceable>command</replaceable></command>

      <arg>--dry-run</arg>

      <arg>--priority <group choice="req">

        <arg>low</arg>

        <arg>normal</arg>

        <arg>high</arg>

      </group></arg>

    </cmdsynopsis>

    <para>

      The <option>--dry-run</option> option can be used to check whether an

      operation would succeed.

    </para>

    <para>

      The option <option>--priority</option> sets the priority for opcodes

      submitted by the command.

    </para>

  </refsect1>

  &footer;

</refentry>

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