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    <h1 >Storage Management</h1>
    <p>
This page describes the backends for the storage management capabilities in
libvirt.
</p>
    <ul>
      <li>
        <a href="#StorageBackendDir">Directory backend</a>
      </li>
      <li>
        <a href="#StorageBackendFS">Local filesystem backend</a>
      </li>
      <li>
        <a href="#StorageBackendNetFS">Network filesystem backend</a>
      </li>
      <li>
        <a href="#StorageBackendLogical">Logical backend</a>
      </li>
      <li>
        <a href="#StorageBackendDisk">Disk backend</a>
      </li>
      <li>
        <a href="#StorageBackendISCSI">iSCSI backend</a>
      </li>
    </ul>

    <h2><a name="StorageBackendDir" id="StorageBackendDir">Directory pool</a></h2>
    <p>
      A pool with a type of <code>dir</code> provides the means to manage
      files within a directory. The files can be fully allocated raw files,
      sparsely allocated raw files, or one of the special disk formats
      such as <code>qcow</code>,<code>qcow2</code>,<code>vmdk</code>,
      <code>cow</code>, etc as supported  by the <code>qemu-img</code>
      program. If the directory does not exist at the time the pool is
      defined, the <code>build</code> operation can be used to create it.
    </p>

    <h3>Example pool input definition</h3>
    <pre>
      &lt;pool type="dir"&gt;
        &lt;name&gt;virtimages&lt;/name&gt;
        &lt;target&gt;
          &lt;path&gt;/var/lib/virt/images&lt;/path&gt;
        &lt;/target&gt;
      &lt;/pool&gt;
    </pre>

    <h3>Valid pool format types</h3>
    <p>
      The directory pool does not use the pool format type element.
    </p>

    <h3>Valid volume format types</h3>
    <p>
      One of the following options:
    </p>
    <ul>
      <li><code>raw</code>: a plain file</li>
      <li><code>bochs</code>: Bochs disk image format</li>
      <li><code>cloop</code>: compressed loopback disk image format</li>
      <li><code>cow</code>: User Mode Linux disk image format</li>
      <li><code>dmg</code>: Mac disk image format</li>
      <li><code>iso</code>: CDROM disk image format</li>
      <li><code>qcow</code>: QEMU v1 disk image format</li>
      <li><code>qcow2</code>: QEMU v2 disk image format</li>
      <li><code>vmdk</code>: VMWare disk image format</li>
      <li><code>vpc</code>: VirtualPC disk image format</li>
    </ul>
    <p>
      When listing existing volumes all these formats are supported
      natively. When creating new volumes, only a subset may be
      available. The <code>raw</code> type is guaranteed always
      available. The <code>qcow2</code> type can be created if
      either <code>qemu-img</code> or <code>qcow-create</code> tools
      are present. The others are dependent on support of the
      <code>qemu-img</code> tool.

    </p>

    <h2><a name="StorageBackendFS" id="StorageBackendFS">Filesystem pool</a></h2>
    <p>
      This is a variant of the directory pool. Instead of creating a
      directory on an existing mounted filesystem though, it expects
      a source block device to be named. This block device will be
      mounted and files managed in the directory of its mount point.
      It will default to allowing the kernel to automatically discover
      the filesystem type, though it can be specified manually if
      required.
    </p>

    <h3>Example pool input</h3>
    <pre>
      &lt;pool type="fs"&gt;
        &lt;name&gt;virtimages&lt;/name&gt;
        &lt;source&gt;
          &lt;device path="/dev/VolGroup00/VirtImages"/&gt;
        &lt;/source&gt;
        &lt;target&gt;
          &lt;path&gt;/var/lib/virt/images&lt;/path&gt;
        &lt;/target&gt;
      &lt;/pool&gt;
    </pre>

    <h3>Valid pool format types</h3>
    <p>
      The filesystem pool supports the following formats:
    </p>
    <ul>
      <li><code>auto</code> - automatically determine format</li>
      <li>
        <code>ext2</code>
      </li>
      <li>
        <code>ext3</code>
      </li>
      <li>
        <code>ext4</code>
      </li>
      <li>
        <code>ufs</code>
      </li>
      <li>
        <code>iso9660</code>
      </li>
      <li>
        <code>udf</code>
      </li>
      <li>
        <code>gfs</code>
      </li>
      <li>
        <code>gfs2</code>
      </li>
      <li>
        <code>vfat</code>
      </li>
      <li>
        <code>hfs+</code>
      </li>
      <li>
        <code>xfs</code>
      </li>
    </ul>

    <h3>Valid volume format types</h3>
    <p>
      The valid volume types are the same as for the <code>directory</code>
      pool type.
    </p>


    <h2><a name="StorageBackendNetFS" id="StorageBackendNetFS">Network filesystem pool</a></h2>
    <p>
      This is a variant of the filesystem pool. Instead of requiring
      a local block device as the source, it requires the name of a
      host and path of an exported directory. It will mount this network
      filesystem and manage files within the directory of its mount
      point. It will default to using NFS as the protocol.
    </p>

    <h3>Example pool input</h3>
    <pre>
      &lt;pool type="netfs"&gt;
        &lt;name&gt;virtimages&lt;/name&gt;
        &lt;source&gt;
          &lt;host name="nfs.example.com"/&gt;
          &lt;dir path="/var/lib/virt/images"/&gt;
        &lt;/source&gt;
        &lt;target&gt;
          &lt;path&gt;/var/lib/virt/images&lt;/path&gt;
        &lt;/target&gt;
      &lt;/pool&gt;
    </pre>

    <h3>Valid pool format types</h3>
    <p>
      The network filesystem pool supports the following formats:
    </p>
    <ul>
      <li><code>auto</code> - automatically determine format</li>
      <li>
        <code>nfs</code>
      </li>
    </ul>

    <h3>Valid volume format types</h3>
    <p>
      The valid volume types are the same as for the <code>directory</code>
      pool type.
    </p>


    <h2><a name="StorageBackendLogical" id="StorageBackendLogical">Logical volume pools</a></h2>
    <p>
      This provides a pool based on an LVM volume group. For a
      pre-defined LVM volume group, simply providing the group
      name is sufficient, while to build a new group requires
      providing a list of source devices to serve as physical
      volumes. Volumes will be allocated by carving out chunks
      of storage from the volume group.
    </p>

    <h3>Example pool input</h3>
    <pre>
      &lt;pool type="logical"&gt;
        &lt;name&gt;HostVG&lt;/name&gt;
        &lt;source&gt;
          &lt;device path="/dev/sda1"/&gt;
          &lt;device path="/dev/sdb1"/&gt;
          &lt;device path="/dev/sdc1"/&gt;
        &lt;/source&gt;
        &lt;target&gt;
          &lt;path&gt;/dev/HostVG&lt;/path&gt;
        &lt;/target&gt;
      &lt;/pool&gt;
    </pre>

    <h3>Valid pool format types</h3>
    <p>
      The logical volume pool does not use the pool format type element.
    </p>

    <h3>Valid volume format types</h3>
    <p>
      The logical volume pool does not use the volume format type element.
    </p>


    <h2><a name="StorageBackendDisk" id="StorageBackendDisk">Disk volume pools</a></h2>
    <p>
      This provides a pool based on a physical disk. Volumes are created
      by adding partitions to the disk. Disk pools are have constraints
      on the size and placement of volumes. The 'free extents'
      information will detail the regions which are available for creating
      new volumes. A volume cannot span across 2 different free extents.
    </p>

    <h3>Example pool input</h3>
    <pre>
      &lt;pool type="disk"&gt;
        &lt;name&gt;sda&lt;/name&gt;
        &lt;source&gt;
          &lt;device path='/dev/sda'/&gt;
        &lt;/source&gt;
        &lt;target&gt;
          &lt;path&gt;/dev&lt;/path&gt;
        &lt;/target&gt;
      &lt;/pool&gt;
    </pre>

    <h3>Valid pool format types</h3>
    <p>
      The disk volume pool accepts the following pool format types, representing
      the common partition table types:
    </p>
    <ul>
      <li>
        <code>dos</code>
      </li>
      <li>
        <code>dvh</code>
      </li>
      <li>
        <code>gpt</code>
      </li>
      <li>
        <code>mac</code>
      </li>
      <li>
        <code>bsd</code>
      </li>
      <li>
        <code>pc98</code>
      </li>
      <li>
        <code>sun</code>
      </li>
    </ul>
    <p>
      The <code>dos</code> or <code>gpt</code> formats are recommended for
      best portability - the latter is needed for disks larger than 2TB.
    </p>

    <h3>Valid volume format types</h3>
    <p>
      The disk volume pool accepts the following volume format types, representing
      the common partition entry types:
    </p>
    <ul>
      <li>
        <code>none</code>
      </li>
      <li>
        <code>linux</code>
      </li>
      <li>
        <code>fat16</code>
      </li>
      <li>
        <code>fat32</code>
      </li>
      <li>
        <code>linux-swap</code>
      </li>
      <li>
        <code>linux-lvm</code>
      </li>
      <li>
        <code>linux-raid</code>
      </li>
      <li>
        <code>extended</code>
      </li>
    </ul>


    <h2><a name="StorageBackendISCSI" id="StorageBackendISCSI">iSCSI volume pools</a></h2>
    <p>
      This provides a pool based on an iSCSI target. Volumes must be
      pre-allocated on the iSCSI server, and cannot be created via
      the libvirt APIs. Since /dev/XXX names may change each time libvirt
      logs into the iSCSI target, it is recommended to configure the pool
      to use <code>/dev/disk/by-path</code> or <code>/dev/disk/by-id</code>
      for the target path. These provide persistent stable naming for LUNs
    </p>

    <h3>Example pool input</h3>
    <pre>
      &lt;pool type="iscsi"&gt;
        &lt;name&gt;virtimages&lt;/name&gt;
        &lt;source&gt;
          &lt;host name="iscsi.example.com"/&gt;
          &lt;device path="demo-target"/&gt;
        &lt;/source&gt;
        &lt;target&gt;
          &lt;path&gt;/dev/disk/by-path&lt;/path&gt;
        &lt;/target&gt;
      &lt;/pool&gt;
    </pre>

    <h3>Valid pool format types</h3>
    <p>
      The iSCSI volume pool does not use the pool format type element.
    </p>

    <h3>Valid volume format types</h3>
    <p>
      The iSCSI volume pool does not use the volume format type element.
    </p>
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