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3888dcaa67
We documented this almost everywhere, but missed it on several places. https://bugzilla.redhat.com/show_bug.cgi?id=1208763
714 lines
35 KiB
XML
714 lines
35 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<body>
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<h1>Storage pool and volume XML format</h1>
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<ul id="toc"></ul>
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<h2><a name="StoragePool">Storage pool XML</a></h2>
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<p>
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Although all storage pool backends share the same public APIs and
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XML format, they have varying levels of capabilities. Some may
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allow creation of volumes, others may only allow use of pre-existing
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volumes. Some may have constraints on volume size, or placement.
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</p>
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<p>
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The top level tag for a storage pool document is 'pool'. It has
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a single attribute <code>type</code>, which is one of <code>dir</code>,
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<code>fs</code>, <code>netfs</code>, <code>disk</code>,
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<code>iscsi</code>, <code>logical</code>, <code>scsi</code>
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(all <span class="since">since 0.4.1</span>), <code>mpath</code>
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(<span class="since">since 0.7.1</span>), <code>rbd</code>
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(<span class="since">since 0.9.13</span>), <code>sheepdog</code>
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(<span class="since">since 0.10.0</span>),
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<code>gluster</code> (<span class="since">since
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1.2.0</span>) or <code>zfs</code> (<span class="since">since
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1.2.8</span>). This corresponds to the
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storage backend drivers listed further along in this document.
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</p>
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<h3><a name="StoragePoolFirst">General metadata</a></h3>
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<pre>
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<pool type="iscsi">
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<name>virtimages</name>
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<uuid>3e3fce45-4f53-4fa7-bb32-11f34168b82b</uuid>
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<allocation>10000000</allocation>
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<capacity>50000000</capacity>
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<available>40000000</available>
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...</pre>
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<dl>
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<dt><code>name</code></dt>
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<dd>Providing a name for the pool which is unique to the host.
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This is mandatory when defining a pool. <span class="since">Since 0.4.1</span></dd>
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<dt><code>uuid</code></dt>
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<dd>Providing an identifier for the pool which is globally unique.
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This is optional when defining a pool, a UUID will be generated if
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omitted. <span class="since">Since 0.4.1</span></dd>
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<dt><code>allocation</code></dt>
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<dd>Providing the total storage allocation for the pool. This may
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be larger than the sum of the allocation of all volumes due to
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metadata overhead. This value is in bytes. This is not applicable
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when creating a pool. <span class="since">Since 0.4.1</span></dd>
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<dt><code>capacity</code></dt>
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<dd>Providing the total storage capacity for the pool. Due to
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underlying device constraints it may not be possible to use the
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full capacity for storage volumes. This value is in bytes. This
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is not applicable when creating a pool. <span class="since">Since 0.4.1</span></dd>
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<dt><code>available</code></dt>
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<dd>Providing the free space available for allocating new volumes
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in the pool. Due to underlying device constraints it may not be
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possible to allocate the entire free space to a single volume.
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This value is in bytes. This is not applicable when creating a
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pool. <span class="since">Since 0.4.1</span></dd>
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</dl>
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<h3><a name="StoragePoolSource">Source elements</a></h3>
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<p>
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A single <code>source</code> element is contained within the top level
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<code>pool</code> element. This tag is used to describe the source of
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the storage pool. The set of child elements that it will contain
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depend on the pool type, but come from the following child elements:
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</p>
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<pre>
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...
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<source>
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<host name="iscsi.example.com"/>
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<device path="demo-target"/>
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<auth type='chap' username='myname'>
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<secret usage='mycluster_myname'/>
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</auth>
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<vendor name="Acme"/>
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<product name="model"/>
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</source>
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...</pre>
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<pre>
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...
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<source>
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<adapter type='scsi_host' name='scsi_host1'/>
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</source>
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...</pre>
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<pre>
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...
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<source>
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<adapter type='scsi_host'>
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<parentaddr unique_id='1'>
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<address domain='0x0000' bus='0x00' slot='0x1f' addr='0x2'/>
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</parentaddr>
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</adapter>
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</source>
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...</pre>
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<pre>
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...
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<source>
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<adapter type='fc_host' parent='scsi_host5' wwnn='20000000c9831b4b' wwpn='10000000c9831b4b'/>
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</source>
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...</pre>
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<dl>
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<dt><code>device</code></dt>
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<dd>Provides the source for pools backed by physical devices
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(pool types <code>fs</code>, <code>logical</code>, <code>disk</code>,
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<code>iscsi</code>, <code>zfs</code>).
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May be repeated multiple times depending on backend driver. Contains
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a single attribute <code>path</code> which is the fully qualified
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path to the block device node. <span class="since">Since 0.4.1</span></dd>
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<dt><code>dir</code></dt>
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<dd>Provides the source for pools backed by directories (pool
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type <code>dir</code>), or optionally to select a subdirectory
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within a pool that resembles a filesystem (pool
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type <code>gluster</code>). May
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only occur once. Contains a single attribute <code>path</code>
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which is the fully qualified path to the backing directory.
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<span class="since">Since 0.4.1</span></dd>
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<dt><code>adapter</code></dt>
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<dd>Provides the source for pools backed by SCSI adapters (pool
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type <code>scsi</code>). May only occur once.
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<dl>
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<dt><code>name</code></dt>
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<dd>The SCSI adapter name (e.g. "scsi_host1", although a name
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such as "host1" is still supported for backwards compatibility,
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it is not recommended). The scsi_host name to be used can be
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determined from the output of a <code>virsh nodedev-list
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scsi_host</code> command followed by a combination of
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<code>lspci</code> and <code>virsh nodedev-dumpxml
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scsi_hostN</code> commands to find the <code>scsi_hostN</code>
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to be used. <span class="since">Since 0.6.2</span>
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<p>
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It is further recommended to utilize the
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<code>parentaddr</code> element since it's possible to have
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the path to which the scsi_hostN uses change between system
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reboots. <span class="since">Since 1.2.7</span>
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</p>
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</dd>
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</dl>
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<dl>
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<dt><code>type</code></dt>
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<dd>Specifies the adapter type. Valid values are "scsi_host" or
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"fc_host". If omitted and the <code>name</code> attribute is
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specified, then it defaults to "scsi_host". To keep backwards
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compatibility, this attribute is optional <b>only</b> for the
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"scsi_host" adapter, but is mandatory for the "fc_host" adapter.
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<span class="since">Since 1.0.5</span>
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A "fc_host" capable scsi_hostN can be determined by using
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<code>virsh nodedev-list --cap fc_host</code>.
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<span class="since">Since 1.2.8</span>
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<p>
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Note: Regardless of whether a "scsi_host" adapter type is defined
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using a <code>name</code> or a <code>parentaddr</code>, it
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should refer to a real scsi_host adapter as found through a
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<code>virsh nodedev-list scsi_host</code> and <code>virsh
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nodedev-dumpxml scsi_hostN</code> on one of the scsi_host's
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displayed. It should not refer to a "fc_host" capable scsi_hostN
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nor should it refer to the vHBA created for some "fc_host"
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adapter. For a vHBA the <code>nodedev-dumpxml</code>
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output parent setting will be the "fc_host" capable scsi_hostN
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value. Additionally, do not refer to an iSCSI scsi_hostN for the
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"scsi_host" source. An iSCSI scsi_hostN's
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<code>nodedev-dumpxml</code> output parent field is generally
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"computer". This is a libvirt created parent value indicating
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no parent was defined for the node device.
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</p>
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</dd>
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</dl>
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<dl>
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<dt><code>wwnn</code> and <code>wwpn</code></dt>
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<dd>The "World Wide Node Name" (<code>wwnn</code>) and "World Wide
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Port Name" (<code>wwpn</code>) are used by the "fc_host" adapter
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to uniquely identify the device in the Fibre Channel storage fabric
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(the device can be either a HBA or vHBA). Both wwnn and wwpn should
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be specified. Use the command 'virsh nodedev-dumpxml' to determine
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how to set the values for the wwnn/wwpn of a (v)HBA. The wwnn and
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wwpn have very specific numerical format requirements based on the
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hypervisor being used, thus care should be taken if you decide to
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generate your own to follow the standards; otherwise, the pool
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will fail to start with an opaque error message indicating failure
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to write to the vport_create file during vport create/delete due
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to "No such file or directory".
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<span class="since">Since 1.0.4</span>
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</dd>
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</dl>
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<dl>
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<dt><code>parent</code></dt>
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<dd>Used by the "fc_host" adapter type to optionally specify the
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parent scsi_host device defined in the
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<a href="formatnode.html">Node Device</a> database as the
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<a href="http://wiki.libvirt.org/page/NPIV_in_libvirt">NPIV</a>
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virtual Host Bus Adapter (vHBA). The value provided must be
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a vport capable scsi_host. The value is not the scsi_host of
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the vHBA created by 'virsh nodedev-create', rather it is
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the parent of that vHBA. If the value is not provided, libvirt
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will determine the parent based either finding the wwnn,wwpn
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defined for an existing scsi_host or by creating a vHBA. Providing
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the parent attribute is also useful for the duplicate pool
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definition checks. This is more important in environments where
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both the "fc_host" and "scsi_host" source adapter pools are being
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used in order to ensure a new definition doesn't duplicate using
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the scsi_hostN of some existing storage pool.
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<span class="since">Since 1.0.4</span>
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</dd>
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<dt><code>managed</code></dt>
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<dd>An optional attribute to instruct the SCSI storage backend to
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manage destroying the vHBA when the pool is destroyed. For
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configurations that do not provide an already created vHBA
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from a 'virsh nodedev-create', libvirt will set this property
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to "yes". For configurations that have already created a vHBA
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via 'virsh nodedev-create' and are using the wwnn/wwpn from
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that vHBA and optionally the scsi_host parent, setting this
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attribute to "yes" will allow libvirt to destroy the node device
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when the pool is destroyed. If this attribute is set to "no" or
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not defined in the XML, then libvirt will not destroy the vHBA.
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<span class="since">Since 1.2.11</span>
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</dd>
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</dl>
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<dl>
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<dt><code>parentaddr</code></dt>
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<dd>Used by the "scsi_host" adapter type instead of the
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<code>name</code> attribute to more uniquely identify the
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SCSI host. Using a combination of the <code>unique_id</code>
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attribute and the <code>address</code> element to formulate
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a PCI address, a search will be performed of the
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<code>/sys/class/scsi_host/hostNN</code> links for a
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matching PCI address with a matching <code>unique_id</code>
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value in the <code>/sys/class/scsi_host/hostNN/unique_id</code>
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file. The value in the "unique_id" file will be unique enough
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for the specific PCI address. The <code>hostNN</code> will be
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used by libvirt as the basis to define which SCSI host is to
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be used for the currently booted system.
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<span class="since">Since 1.2.7</span>
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<dl>
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<dt><code>address</code></dt>
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<dd>The PCI address of the scsi_host device to be used. Using
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a PCI address provides consistent naming across system reboots
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and kernel reloads. The address will have four attributes:
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<code>domain</code> (a 2-byte hex integer, not currently used
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by qemu), <code>bus</code> (a hex value between 0 and 0xff,
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inclusive), <code>slot</code> (a hex value between 0x0 and
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0x1f, inclusive), and <code>function</code> (a value between
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0 and 7, inclusive). The PCI address can be determined by
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listing the <code>/sys/bus/pci/devices</code> and the
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<code>/sys/class/scsi_host</code> directories in order to
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find the expected scsi_host device. The address will be
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provided in a format such as "0000:00:1f:2" which can be
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used to generate the expected PCI address
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"domain='0x0000' bus='0x00' slot='0x1f' function='0x0'".
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Optionally, using the combination of the commands 'virsh
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nodedev-list scsi_host' and 'virsh nodedev-dumpxml' for a
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specific list entry and converting the resulting
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<code>path</code> element as the basis to formulate the
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correctly formatted PCI address.
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</dd>
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</dl>
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<dl>
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<dt><code>unique_id</code></dt>
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<dd>Required <code>parentaddr</code> attribute used to determine
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which of the scsi_host adapters for the provided PCI address
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should be used. The value is determine by contents of the
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<code>unique_id</code> file for the specific scsi_host adapter.
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For a PCI address of "0000:00:1f:2", the unique identifer files
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can be found using the command
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<code>find -H /sys/class/scsi_host/host*/unique_id |
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xargs grep '[0-9]'</code>. Optionally, the
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<code>virsh nodedev-dumpxml scsi_hostN</code>' of a
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specific scsi_hostN list entry will list the
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<code>unique_id</code> value.
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</dd>
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</dl>
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</dd>
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</dl>
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</dd>
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<dt><code>host</code></dt>
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<dd>Provides the source for pools backed by storage from a
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remote server (pool types <code>netfs</code>, <code>iscsi</code>,
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<code>rbd</code>, <code>sheepdog</code>, <code>gluster</code>). Will be
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used in combination with a <code>directory</code>
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or <code>device</code> element. Contains an attribute <code>name</code>
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which is the hostname or IP address of the server. May optionally
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contain a <code>port</code> attribute for the protocol specific
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port number. <span class="since">Since 0.4.1</span></dd>
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<dt><code>auth</code></dt>
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<dd>If present, the <code>auth</code> element provides the
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authentication credentials needed to access the source by the
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setting of the <code>type</code> attribute (pool
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types <code>iscsi</code>, <code>rbd</code>). The <code>type</code>
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must be either "chap" or "ceph". Use "ceph" for
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Ceph RBD (Rados Block Device) network sources and use "iscsi" for CHAP
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(Challenge-Handshake Authentication Protocol) iSCSI
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targets. Additionally a mandatory attribute
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<code>username</code> identifies the username to use during
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authentication as well as a sub-element <code>secret</code> with
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a mandatory attribute <code>type</code>, to tie back to a
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<a href="formatsecret.html">libvirt secret object</a> that
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holds the actual password or other credentials. The domain XML
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intentionally does not expose the password, only the reference
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to the object that manages the password.
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The <code>secret</code> element requires either a <code>uuid</code>
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attribute with the UUID of the secret object or a <code>usage</code>
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attribute matching the key that was specified in the
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secret object. <span class="since">Since 0.9.7 for "ceph" and
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1.1.1 for "chap"</span>
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</dd>
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<dt><code>name</code></dt>
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<dd>Provides the source for pools backed by storage from a
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named element (pool types <code>logical</code>, <code>rbd</code>,
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<code>sheepdog</code>, <code>gluster</code>). Contains a
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string identifier.
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<span class="since">Since 0.4.5</span></dd>
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<dt><code>format</code></dt>
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<dd>Provides information about the format of the pool (pool
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types <code>fs</code>, <code>netfs</code>, <code>disk</code>,
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<code>logical</code>). This
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contains a single attribute <code>type</code> whose value is
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backend specific. This is typically used to indicate filesystem
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type, or network filesystem type, or partition table type, or
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LVM metadata type. All drivers are required to have a default
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value for this, so it is optional. <span class="since">Since 0.4.1</span></dd>
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<dt><code>vendor</code></dt>
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<dd>Provides optional information about the vendor of the
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storage device. This contains a single
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attribute <code>name</code> whose value is backend
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specific. <span class="since">Since 0.8.4</span></dd>
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<dt><code>product</code></dt>
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<dd>Provides an optional product name of the storage device.
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This contains a single attribute <code>name</code> whose value
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is backend specific. <span class="since">Since 0.8.4</span></dd>
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</dl>
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<h3><a name="StoragePoolTarget">Target elements</a></h3>
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<p>
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A single <code>target</code> element is contained within the top level
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<code>pool</code> element for some types of pools (pool
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types <code>dir</code>, <code>fs</code>, <code>netfs</code>,
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<code>logical</code>, <code>disk</code>, <code>iscsi</code>,
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<code>scsi</code>, <code>mpath</code>). This tag is used to
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describe the mapping of
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the storage pool into the host filesystem. It can contain the following
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child elements:
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</p>
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<pre>
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...
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<target>
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<path>/dev/disk/by-path</path>
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<permissions>
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<owner>107</owner>
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<group>107</group>
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<mode>0744</mode>
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<label>virt_image_t</label>
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</permissions>
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<timestamps>
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<atime>1341933637.273190990</atime>
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<mtime>1341930622.047245868</mtime>
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<ctime>1341930622.047245868</ctime>
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</timestamps>
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<encryption type='...'>
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...
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</encryption>
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</target>
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</pool></pre>
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<dl>
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<dt><code>path</code></dt>
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<dd>Provides the location at which the pool will be mapped into
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the local filesystem namespace, as an absolute path. For a
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filesystem/directory based pool it will be a fully qualified name of
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the directory in which volumes will be created. For device based pools
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it will be a fully qualified name of the directory in which
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devices nodes exist. For the latter <code>/dev/</code> may seem
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like the logical choice, however, devices nodes there are not
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guaranteed stable across reboots, since they are allocated on
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demand. It is preferable to use a stable location such as one
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of the <code>/dev/disk/by-{path|id|uuid|label}</code> locations.
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<span class="since">Since 0.4.1</span>
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</dd>
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<dt><code>permissions</code></dt>
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<dd>This is currently only useful for directory or filesystem based
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pools, which are mapped as a directory into the local filesystem
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namespace. It provides information about the permissions to use for the
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final directory when the pool is built. The
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<code>mode</code> element contains the octal permission set. The
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<code>owner</code> element contains the numeric user ID. The <code>group</code>
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element contains the numeric group ID. The <code>label</code> element
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contains the MAC (eg SELinux) label string.
|
|
<span class="since">Since 0.4.1</span>
|
|
</dd>
|
|
<dt><code>timestamps</code></dt>
|
|
<dd>Provides timing information about the volume. Up to four
|
|
sub-elements are present,
|
|
where <code>atime</code>, <code>btime</code>, <code>ctime</code>
|
|
and <code>mtime</code> hold the access, birth, change and
|
|
modification time of the volume, where known. The used time
|
|
format is <seconds>.<nanoseconds> since the
|
|
beginning of the epoch (1 Jan 1970). If nanosecond resolution
|
|
is 0 or otherwise unsupported by the host OS or filesystem,
|
|
then the nanoseconds part is omitted. This is a readonly
|
|
attribute and is ignored when creating a volume.
|
|
<span class="since">Since 0.10.0</span>
|
|
</dd>
|
|
<dt><code>encryption</code></dt>
|
|
<dd>If present, specifies how the volume is encrypted. See
|
|
the <a href="formatstorageencryption.html">Storage Encryption</a> page
|
|
for more information.
|
|
</dd>
|
|
</dl>
|
|
|
|
<h3><a name="StoragePoolExtents">Device extents</a></h3>
|
|
|
|
<p>
|
|
If a storage pool exposes information about its underlying
|
|
placement / allocation scheme, the <code>device</code> element
|
|
within the <code>source</code> element may contain information
|
|
about its available extents. Some pools have a constraint that
|
|
a volume must be allocated entirely within a single constraint
|
|
(eg disk partition pools). Thus the extent information allows an
|
|
application to determine the maximum possible size for a new
|
|
volume
|
|
</p>
|
|
<p>
|
|
For storage pools supporting extent information, within each
|
|
<code>device</code> element there will be zero or more <code>freeExtent</code>
|
|
elements. Each of these elements contains two attributes, <code>start</code>
|
|
and <code>end</code> which provide the boundaries of the extent on the
|
|
device, measured in bytes. <span class="since">Since 0.4.1</span>
|
|
</p>
|
|
|
|
<h2><a name="StorageVol">Storage volume XML</a></h2>
|
|
<p>
|
|
A storage volume will generally be either a file or a device
|
|
node; <span class="since">since 1.2.0</span>, an optional
|
|
output-only attribute <code>type</code> lists the actual type
|
|
(file, block, dir, network, or netdir), which is also available
|
|
from <code>virStorageVolGetInfo()</code>. The storage volume
|
|
XML format is available <span class="since">since 0.4.1</span>
|
|
</p>
|
|
|
|
<h3><a name="StorageVolFirst">General metadata</a></h3>
|
|
|
|
<pre>
|
|
<volume type='file'>
|
|
<name>sparse.img</name>
|
|
<key>/var/lib/xen/images/sparse.img</key>
|
|
<allocation>0</allocation>
|
|
<capacity unit="T">1</capacity>
|
|
...</pre>
|
|
|
|
<dl>
|
|
<dt><code>name</code></dt>
|
|
<dd>Providing a name for the volume which is unique to the pool.
|
|
This is mandatory when defining a volume. For a disk pool, the
|
|
name must be combination of the <code>source</code> device path
|
|
device and next partition number to be created. For example, if
|
|
the <code>source</code> device path is /dev/sdb and there are no
|
|
partitions on the disk, then the name must be sdb1 with the next
|
|
name being sdb2 and so on.
|
|
<span class="since">Since 0.4.1</span></dd>
|
|
<dt><code>key</code></dt>
|
|
<dd>Providing an identifier for the volume which identifies a
|
|
single volume. In some cases it's possible to have two distinct keys
|
|
identifying a single volume. This field cannot be set when creating
|
|
a volume: it is always generated.
|
|
<span class="since">Since 0.4.1</span></dd>
|
|
<dt><code>allocation</code></dt>
|
|
<dd>Providing the total storage allocation for the volume. This
|
|
may be smaller than the logical capacity if the volume is sparsely
|
|
allocated. It may also be larger than the logical capacity if the
|
|
volume has substantial metadata overhead. This value is in bytes.
|
|
If omitted when creating a volume, the volume will be fully
|
|
allocated at time of creation. If set to a value smaller than the
|
|
capacity, the pool has the <strong>option</strong> of deciding
|
|
to sparsely allocate a volume. It does not have to honour requests
|
|
for sparse allocation though. Different types of pools may treat
|
|
sparse volumes differently. For example, the <code>logical</code>
|
|
pool will not automatically expand volume's allocation when it
|
|
gets full; the user is responsible for doing that or configuring
|
|
dmeventd to do so automatically.<br/>
|
|
<br/>
|
|
By default this is specified in bytes, but an optional attribute
|
|
<code>unit</code> can be specified to adjust the passed value.
|
|
Values can be: 'B' or 'bytes' for bytes, 'KB' (kilobytes,
|
|
10<sup>3</sup> or 1000 bytes), 'K' or 'KiB' (kibibytes,
|
|
2<sup>10</sup> or 1024 bytes), 'MB' (megabytes, 10<sup>6</sup>
|
|
or 1,000,000 bytes), 'M' or 'MiB' (mebibytes, 2<sup>20</sup>
|
|
or 1,048,576 bytes), 'GB' (gigabytes, 10<sup>9</sup> or
|
|
1,000,000,000 bytes), 'G' or 'GiB' (gibibytes, 2<sup>30</sup>
|
|
or 1,073,741,824 bytes), 'TB' (terabytes, 10<sup>12</sup> or
|
|
1,000,000,000,000 bytes), 'T' or 'TiB' (tebibytes,
|
|
2<sup>40</sup> or 1,099,511,627,776 bytes), 'PB' (petabytes,
|
|
10<sup>15</sup> or 1,000,000,000,000,000 bytes), 'P' or 'PiB'
|
|
(pebibytes, 2<sup>50</sup> or 1,125,899,906,842,624 bytes),
|
|
'EB' (exabytes, 10<sup>18</sup> or 1,000,000,000,000,000,000
|
|
bytes), or 'E' or 'EiB' (exbibytes, 2<sup>60</sup> or
|
|
1,152,921,504,606,846,976 bytes). <span class="since">Since
|
|
0.4.1, multi-character <code>unit</code> since
|
|
0.9.11</span></dd>
|
|
<dt><code>capacity</code></dt>
|
|
<dd>Providing the logical capacity for the volume. This value is
|
|
in bytes by default, but a <code>unit</code> attribute can be
|
|
specified with the same semantics as for <code>allocation</code>
|
|
This is compulsory when creating a volume.
|
|
<span class="since">Since 0.4.1</span></dd>
|
|
<dt><code>source</code></dt>
|
|
<dd>Provides information about the underlying storage allocation
|
|
of the volume. This may not be available for some pool types.
|
|
<span class="since">Since 0.4.1</span></dd>
|
|
<dt><code>target</code></dt>
|
|
<dd>Provides information about the representation of the volume
|
|
on the local host. <span class="since">Since 0.4.1</span></dd>
|
|
</dl>
|
|
|
|
<h3><a name="StorageVolTarget">Target elements</a></h3>
|
|
|
|
<p>
|
|
A single <code>target</code> element is contained within the top level
|
|
<code>volume</code> element. This tag is used to describe the mapping of
|
|
the storage volume into the host filesystem. It can contain the following
|
|
child elements:
|
|
</p>
|
|
|
|
<pre>
|
|
...
|
|
<target>
|
|
<path>/var/lib/virt/images/sparse.img</path>
|
|
<format type='qcow2'/>
|
|
<permissions>
|
|
<owner>107</owner>
|
|
<group>107</group>
|
|
<mode>0744</mode>
|
|
<label>virt_image_t</label>
|
|
</permissions>
|
|
<compat>1.1</compat>
|
|
<nocow/>
|
|
<features>
|
|
<lazy_refcounts/>
|
|
</features>
|
|
</target></pre>
|
|
|
|
<dl>
|
|
<dt><code>path</code></dt>
|
|
<dd>Provides the location at which the volume can be accessed on
|
|
the local filesystem, as an absolute path. This is a readonly
|
|
attribute, so shouldn't be specified when creating a volume.
|
|
<span class="since">Since 0.4.1</span></dd>
|
|
<dt><code>format</code></dt>
|
|
<dd>Provides information about the pool specific volume format.
|
|
For disk pools it will provide the partition table format type, but is
|
|
not preserved after a pool refresh or libvirtd restart. Use extended
|
|
in order to create an extended disk extent partition. For filesystem
|
|
or directory pools it will provide the file format type, eg cow,
|
|
qcow, vmdk, raw. If omitted when creating a volume, the pool's
|
|
default format will be used. The actual format is specified via
|
|
the <code>type</code> attribute. Consult the
|
|
<a href="storage.html">storage driver page</a> for the list of valid
|
|
volume format type values for each specific pool. The
|
|
<code>format</code> will be ignored on input for pools without a
|
|
volume format type value and the default pool format will be used.
|
|
<span class="since">Since 0.4.1</span></dd>
|
|
<dt><code>permissions</code></dt>
|
|
<dd>Provides information about the default permissions to use
|
|
when creating volumes. This is currently only useful for directory
|
|
or filesystem based pools, where the volumes allocated are simple
|
|
files. For pools where the volumes are device nodes, the hotplug
|
|
scripts determine permissions. It contains 4 child elements. The
|
|
<code>mode</code> element contains the octal permission set. The
|
|
<code>owner</code> element contains the numeric user ID. The <code>group</code>
|
|
element contains the numeric group ID. The <code>label</code> element
|
|
contains the MAC (eg SELinux) label string.
|
|
<span class="since">Since 0.4.1</span>
|
|
</dd>
|
|
<dt><code>compat</code></dt>
|
|
<dd>Specify compatibility level. So far, this is only used for
|
|
<code>type='qcow2'</code> volumes. Valid values are <code>0.10</code>
|
|
and <code>1.1</code> so far, specifying QEMU version the images should
|
|
be compatible with. If the <code>feature</code> element is present,
|
|
1.1 is used.
|
|
<span class="since">Since 1.1.0</span> If omitted, 0.10 is used.
|
|
<span class="since">Since 1.1.2</span>
|
|
</dd>
|
|
<dt><code>nocow</code></dt>
|
|
<dd>Turn off COW of the newly created volume. So far, this is only valid
|
|
for a file image in btrfs file system. It will improve performance when
|
|
the file image is used in VM. To create non-raw file images, it
|
|
requires QEMU version since 2.1. <span class="since">Since 1.2.7</span>
|
|
</dd>
|
|
<dt><code>features</code></dt>
|
|
<dd>Format-specific features. Only used for <code>qcow2</code> now.
|
|
Valid sub-elements are:
|
|
<ul>
|
|
<li><code><lazy_refcounts/></code> - allow delayed reference
|
|
counter updates. <span class="since">Since 1.1.0</span></li>
|
|
</ul>
|
|
</dd>
|
|
</dl>
|
|
|
|
<h3><a name="StorageVolBacking">Backing store elements</a></h3>
|
|
|
|
<p>
|
|
A single <code>backingStore</code> element is contained within the top level
|
|
<code>volume</code> element. This tag is used to describe the optional copy
|
|
on write, backing store for the storage volume. It can contain the following
|
|
child elements:
|
|
</p>
|
|
|
|
<pre>
|
|
...
|
|
<backingStore>
|
|
<path>/var/lib/virt/images/master.img</path>
|
|
<format type='raw'/>
|
|
<permissions>
|
|
<owner>107</owner>
|
|
<group>107</group>
|
|
<mode>0744</mode>
|
|
<label>virt_image_t</label>
|
|
</permissions>
|
|
</backingStore>
|
|
</volume></pre>
|
|
|
|
<dl>
|
|
<dt><code>path</code></dt>
|
|
<dd>Provides the location at which the backing store can be accessed on
|
|
the local filesystem, as an absolute path. If omitted, there is no
|
|
backing store for this volume.
|
|
<span class="since">Since 0.6.0</span></dd>
|
|
<dt><code>format</code></dt>
|
|
<dd>Provides information about the pool specific backing store format.
|
|
For disk pools it will provide the partition type. For filesystem
|
|
or directory pools it will provide the file format type, eg cow,
|
|
qcow, vmdk, raw. The actual format is specified via the type attribute.
|
|
Consult the pool-specific docs for the list of valid
|
|
values. Most file formats require a backing store of the same format,
|
|
however, the qcow2 format allows a different backing store format.
|
|
<span class="since">Since 0.6.0</span></dd>
|
|
<dt><code>permissions</code></dt>
|
|
<dd>Provides information about the permissions of the backing file.
|
|
It contains 4 child elements. The
|
|
<code>mode</code> element contains the octal permission set. The
|
|
<code>owner</code> element contains the numeric user ID. The <code>group</code>
|
|
element contains the numeric group ID. The <code>label</code> element
|
|
contains the MAC (eg SELinux) label string.
|
|
<span class="since">Since 0.6.0</span>
|
|
</dd>
|
|
</dl>
|
|
|
|
<h2><a name="examples">Example configuration</a></h2>
|
|
|
|
<p>
|
|
Here are a couple of examples, for a more complete set demonstrating
|
|
every type of storage pool, consult the <a href="storage.html">storage driver page</a>
|
|
</p>
|
|
|
|
<h3><a name="exampleFile">File based storage pool</a></h3>
|
|
|
|
<pre>
|
|
<pool type="dir">
|
|
<name>virtimages</name>
|
|
<target>
|
|
<path>/var/lib/virt/images</path>
|
|
</target>
|
|
</pool></pre>
|
|
|
|
<h3><a name="exampleISCSI">iSCSI based storage pool</a></h3>
|
|
|
|
<pre>
|
|
<pool type="iscsi">
|
|
<name>virtimages</name>
|
|
<source>
|
|
<host name="iscsi.example.com"/>
|
|
<device path="iqn.2013-06.com.example:iscsi-pool"/>
|
|
<auth type='chap' username='myuser'>
|
|
<secret usage='libvirtiscsi'/>
|
|
</auth>
|
|
</source>
|
|
<target>
|
|
<path>/dev/disk/by-path</path>
|
|
</target>
|
|
</pool></pre>
|
|
|
|
<h3><a name="exampleVol">Storage volume</a></h3>
|
|
|
|
<pre>
|
|
<volume>
|
|
<name>sparse.img</name>
|
|
<allocation>0</allocation>
|
|
<capacity unit="T">1</capacity>
|
|
<target>
|
|
<path>/var/lib/virt/images/sparse.img</path>
|
|
<permissions>
|
|
<owner>107</owner>
|
|
<group>107</group>
|
|
<mode>0744</mode>
|
|
<label>virt_image_t</label>
|
|
</permissions>
|
|
</target>
|
|
</volume></pre>
|
|
</body>
|
|
</html>
|