Skip to content

help.ubuntu-it.org
help.ubuntu-it.org
Switch branch/tag
Find file BlameHistoryPermalink
device-mapper-multipathing.html 13.9 KB
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Device Mapper Multipathing</title>
<link rel="stylesheet" type="text/css" href="it.css">
<script type="text/javascript" src="jquery.js"></script><script type="text/javascript" src="jquery.syntax.js"></script><script type="text/javascript" src="yelp.js"></script><link rel="stylesheet" type="text/css" href="main.css">
<link rel="stylesheet" type="text/css" href="custom.css">
<script type="text/javascript" src="http://ubuntu-it.org/sites/all/themes/light-drupal-theme/js/cookies.js"></script><script type="text/javascript" src="http://ubuntu-it.org/sites/all/themes/light-drupal-theme/js/accessibility.js"></script>
</head>
<body>
<script type="text/javascript">var gaJsHost = (("https:" == document.location.protocol) ? "https://ssl." : "http://www.");
      document.write(unescape("%3Cscript src='" + gaJsHost + "google-analytics.com/ga.js' type='text/javascript'%3E%3C/script%3E"));
      </script><script type="text/javascript">
      try {
      var pageTracker = _gat._getTracker("UA-8147493-2");
      pageTracker._trackPageview();
      } catch(err) {}
      </script><div id="fixed-header">
<div id="header" class="shadowed curved-bottom"><div class="container">
<ul class="links">
<li><a href="http://help.ubuntu-it.org">Documentazione ufficiale</a></li>
<li><a href="http://wiki.ubuntu-it.org/Documentazione/Indice">Guide della comunità</a></li>
<li class="active"><a href="http://help.ubuntu-it.org/12.04/server/serverguide/it/index.html">12.04 LTS</a></li>
</ul>
<div id="logo">
<div id="ubuntu-it-sites">
<a href="http://www.ubuntu-it.org">web </a><a href="http://wiki.ubuntu-it.org">wiki </a><a href="http://forum.ubuntu-it.org">forum </a><a href="http://planet.ubuntu-it.org">planet </a>
</div>
<a href="http://help.ubuntu-it.org" title="Ubuntu - Documentazione ufficiale"><span>help.</span>ubuntu-it
            </a><span>comunità italiana</span>
</div>
<div class="buttons"><div id="accessibility" title="Maggiore focus ai contenuti" onclick="accessibility_toggle();"></div></div>
</div></div>
<div id="subheader"><div class="container"><div class="container-inside"><ul class="links secondary-links">
<li><a href="http://help.ubuntu-it.org/12.04/desktop/index.html" title="Guida utente di Ubuntu 12.04 LTS">Desktop</a></li>
<li class="active"><a href="http://help.ubuntu-it.org/12.04/server/serverguide/it/index.html" title="Guida utente di Ubuntu server 12.04 LTS">Server</a></li>
<li><a href="http://help.ubuntu-it.org/12.04/search.php" title="Ricerna della documentazione di Ubuntu 12.04 LTS">Ricerca</a></li>
</ul></div></div></div>
</div>
<div id="content">
<div id="content-top"></div>
<div class="container">
<div id="tmp-note">Questa guida non è stata ancora completamente tradotta. Se vuoi contribuire alla sua traduzione contatta il <a href="http://wiki.ubuntu-it.org/GruppoTraduzione/" title="Gruppo Traduzione">Gruppo Traduzione</a> di Ubuntu-it.</div>
<div id="search-box"><form action="http://help.ubuntu-it.org/12.04/search.php" id="cse-search-box"><div><input type="text" name="s" value="Cerca ..." onfocus="if(this.value == 'Cerca ...') { this.value = ''; }" onblur="if (this.value == '') {this.value = 'Cerca ...';}"></div></form></div>
<div class="trails"><div class="trail">
<a class="trail" href="index.html" title="Guida a Ubuntu Server">Guida a Ubuntu Server</a> » <a class="trail" href="dm-multipath-chapter.html" title="DM-Multipath">DM-Multipath</a> » </div></div>
<div id="cwt-content"><div id="page">
<div id="content">
<div class="links nextlinks">
<a class="nextlinks-prev" href="dm-multipath-chapter.html" title="DM-Multipath">Indietro</a>  |  <a class="nextlinks-next" href="multipath-devices.html" title="Multipath Devices">Avanti</a>
</div>
<div class="hgroup"><h1 class="title">Device Mapper Multipathing</h1></div>
<div class="region">
<div class="contents"><p class="para">Device mapper multipathing (DM-Multipath) allows you to configure
    multiple I/O paths between server nodes and storage arrays into a single
    device. These I/O paths are physical SAN connections that can include
    separate cables, switches, and controllers. Multipathing aggregates the
    I/O paths, creating a new device that consists of the aggregated paths.
    This chapter provides a summary of the features of DM-Multipath that are
    new for the initial release of Ubuntu Server 12.04. Following that, this
    chapter provides a high-level overview of DM Multipath and its components,
    as well as an overview of DM-Multipath setup.</p></div>
<div class="links sectionlinks"><ul>
<li class="links"><a class="xref" href="device-mapper-multipathing.html#multipath-new-and-changed-features" title="New and Changed Features for Ubuntu Server 12.04">New and Changed Features for Ubuntu Server 12.04</a></li>
<li class="links"><a class="xref" href="device-mapper-multipathing.html#multipath-overview" title="Panoramica">Panoramica</a></li>
<li class="links"><a class="xref" href="device-mapper-multipathing.html#multipath-storage-array-support" title="Storage Array Overview">Storage Array Overview</a></li>
<li class="links"><a class="xref" href="device-mapper-multipathing.html#multipath-dm-multipath-components" title="DM-Multipath components">DM-Multipath components</a></li>
<li class="links"><a class="xref" href="device-mapper-multipathing.html#multipath-dm-multipath-setup-overview" title="DM-Multipath Setup Overview">DM-Multipath Setup Overview</a></li>
</ul></div>
<div class="sect2 sect" id="multipath-new-and-changed-features"><div class="inner">
<div class="hgroup"><h2 class="title">New and Changed Features for Ubuntu Server 12.04</h2></div>
<div class="region">
<div class="contents"><p class="para">Migrated from multipath-0.4.8 to multipath-0.4.9</p></div>
<div class="sect3 sect" id="multipath-migration-from-previous-release"><div class="inner">
<div class="hgroup"><h3 class="title">Migration from 0.4.8</h3></div>
<div class="region"><div class="contents">
<p class="para">The priority checkers are no longer run as standalone binaries,
        but as shared libraries. The key value name for this feature has also
        slightly changed. Copy the attribute named <span class="em em-bold emphasis">prio_callout</span> to <span class="em em-bold emphasis">prio</span>, also modify the argument the name of the
        priority checker, a system path is no longer necessary. Example
        conversion:<div class="screen"><pre class="contents ">device {
        vendor "NEC"
        product "DISK ARRAY"
        prio_callout mpath_prio_alua /dev/%n
        prio    alua
}</pre></div></p>
<p class="para">See Table <a class="xref" href="device-mapper-multipathing.html#priority-checker-conversion-table" title="Priority Checker
          Conversion">Priority Checker
          Conversion</a> for a complete listing</p>
<div class="table">
<a name="priority-checker-conversion-table"></a><div class="title">
<a name="checker-conversion-table"></a><h4><span class="title">Priority Checker
          Conversion</span></h4>
</div>
<table summary="Priority Checker
          Conversion" style="border: solid 1px;">
<thead><tr>
<th style="text-align: center;" class="td-colsep">v0.4.8</th>
<th style="text-align: center;">v0.4.9</th>
</tr></thead>
<tbody>
<tr>
<td class="td-colsep"><span class="em em-bold emphasis">prio_callout mpath_prio_emc
                /dev/%n</span></td>
<td><span class="em em-bold emphasis">prio emc</span></td>
</tr>
<tr class="shade">
<td class="td-colsep"><span class="em em-bold emphasis">prio_callout mpath_prio_alua
                /dev/%n</span></td>
<td><span class="em em-bold emphasis">prio alua</span></td>
</tr>
<tr>
<td class="td-colsep"><span class="em em-bold emphasis">prio_callout mpath_prio_netapp
                /dev/%n</span></td>
<td><span class="em em-bold emphasis">prio netapp</span></td>
</tr>
<tr class="shade">
<td class="td-colsep"><span class="em em-bold emphasis">prio_callout mpath_prio_rdac
                /dev/%n</span></td>
<td><span class="em em-bold emphasis">prio rdac</span></td>
</tr>
<tr>
<td class="td-colsep"><span class="em em-bold emphasis">prio_callout mpath_prio_hp_sw
                /dev/%n</span></td>
<td><span class="em em-bold emphasis">prio hp_sw</span></td>
</tr>
<tr class="shade">
<td class="td-colsep"><span class="em em-bold emphasis">prio_callout
                mpath_prio_hds_modular %b</span></td>
<td><span class="em em-bold emphasis">prio hds</span></td>
</tr>
</tbody>
</table>
</div>
<p class="para">Since the multipath config file parser essentially parses all
        key/value pairs it finds and then makes use of them, it is safe for
        both <span class="em em-bold emphasis">prio_callout</span> and <span class="em em-bold emphasis">prio</span> to coexist and is recommended that the
        <span class="em em-bold emphasis">prio</span> attribute be inserted before
        beginning migration. After which you can safely delete the legacy
        <span class="em em-bold emphasis">prio_calliout</span> attribute without
        interrupting service.</p>
</div></div>
</div></div>
</div>
</div></div>
<div class="sect2 sect" id="multipath-overview"><div class="inner">
<div class="hgroup"><h2 class="title">Panoramica</h2></div>
<div class="region"><div class="contents">
<p class="para">DM-Multipath can be used to provide:</p>
<div class="list itemizedlist"><ul class="list itemizedlist">
<li class="list itemizedlist">
          <p class="para"><span class="em emphasis"> Redundancy </span> DM-Multipath can provide
          failover in an active/passive configuration. In an active/passive
          configuration, only half the paths are used at any time for I/O. If
          any element of an I/O path (the cable, switch, or controller) fails,
          DM-Multipath switches to an alternate path.</p>
        </li>
<li class="list itemizedlist">
          <p class="para"><span class="em emphasis"> Improved Performance </span> Performance
          DM-Multipath can be configured in active/active mode, where I/O is
          spread over the paths in a round-robin fashion. In some
          configurations, DM-Multipath can detect loading on the I/O paths and
          dynamically re-balance the load.</p>
        </li>
</ul></div>
</div></div>
</div></div>
<div class="sect2 sect" id="multipath-storage-array-support"><div class="inner">
<div class="hgroup"><h2 class="title">Storage Array Overview</h2></div>
<div class="region"><div class="contents"><p class="para">By default, DM-Multipath includes support for the most common
      storage arrays that support DM-Multipath. The supported devices can be
      found in the multipath.conf.defaults file. If your storage array
      supports DM-Multipath and is not configured by default in this file, you
      may need to add them to the DM-Multipath configuration file,
      multipath.conf. For information on the DM-Multipath configuration file,
      see Section, <a class="link" href="multipath-dm-multipath-config-file.html" title="The DM-Multipath Configuration File">The
      DM-Multipath Configuration File</a>. Some storage arrays require
      special handling of I/O errors and path switching. These require
      separate hardware handler kernel modules.</p></div></div>
</div></div>
<div class="sect2 sect" id="multipath-dm-multipath-components"><div class="inner">
<div class="hgroup"><h2 class="title">DM-Multipath components</h2></div>
<div class="region"><div class="contents"><p class="para">Table “<a class="link" href=".html#multipath-components-table" title="">DM-Multipath
      Components”</a> describes the components of the DM-Multipath package.
      </p></div></div>
</div></div>
<div class="sect2 sect" id="multipath-dm-multipath-setup-overview"><div class="inner">
<div class="hgroup"><h2 class="title">DM-Multipath Setup Overview</h2></div>
<div class="region"><div class="contents"><p class="para">DM-Multipath includes compiled-in default settings that are
      suitable for common multipath configurations. Setting up DM-multipath is
      often a simple procedure. The basic procedure for configuring your
      system with DM-Multipath is as follows: <div class="list orderedlist"><ol class="list orderedlist">
<li class="list orderedlist">
            <p class="para">Install the <span class="em em-bold emphasis">multipath-tools</span>
            and <span class="em em-bold emphasis">multipath-tools-boot</span>
            packages</p>
          </li>
<li class="list orderedlist">
            <p class="para">Create an empty config file, <span class="file filename">/etc/multipath.conf</span>, that
            re-defines the <a class="link" href="multipath-setting-up-dm-multipath.html#multipath-skel-config" title="">following</a></p>
          </li>
<li class="list orderedlist">
            <p class="para">If necessary, edit the <span class="em em-bold emphasis">multipath.conf</span> configuration file to modify
            default values and save the updated file.</p>
          </li>
<li class="list orderedlist">
            <p class="para">Start the multipath daemon</p>
          </li>
<li class="list orderedlist">
            <p class="para">Update initial ramdisk</p>
          </li>
</ol></div> For detailed setup instructions for multipath
      configuration see Section, <a class="link" href="multipath-setting-up-dm-multipath.html#multipath-setup-overview" title="Setting Up DM-Multipath">Setting Up
      DM-Multipath</a>.</p></div></div>
</div></div>
</div>
<div class="links nextlinks">
<a class="nextlinks-prev" href="dm-multipath-chapter.html" title="DM-Multipath">Indietro</a>  |  <a class="nextlinks-next" href="multipath-devices.html" title="Multipath Devices">Avanti</a>
</div>
<div class="clear"></div>
</div>
<div id="pagebottom"></div>
</div></div>
</div>
<div id="content-bottom"></div>
</div>
<div id="footer"><div class="container">
<div id="ubuntulinks">Ubuntu e Canonical sono marchi registrati da Canonical Ltd. <br>
Questa opera è pubblicata sotto una <span style="text-decoration: underline;"><a href="http://help.ubuntu-it.org/legal.html">licenza</a></span> Creative Commons.
</div>
<div id="pagebottom"></div>
</div></div>
</body>
</html>