mirror of
https://gitlab.com/libvirt/libvirt.git
synced 2024-07-11 12:25:52 +00:00
394 lines
18 KiB
HTML
394 lines
18 KiB
HTML
<html>
|
|
<body>
|
|
<h1>Storage pool and volume XML format</h1>
|
|
|
|
<ul id="toc"></ul>
|
|
|
|
<h2><a name="StoragePool">Storage pool XML</a></h2>
|
|
|
|
<p>
|
|
Although all storage pool backends share the same public APIs and
|
|
XML format, they have varying levels of capabilities. Some may
|
|
allow creation of volumes, others may only allow use of pre-existing
|
|
volumes. Some may have constraints on volume size, or placement.
|
|
</p>
|
|
<p>
|
|
The is the top level tag for a storage pool document is 'pool'. It has
|
|
a single attribute <code>type</code>, which is one of <code>dir</code>,
|
|
<code>fs</code>,<code>netfs</code>,<code>disk</code>,<code>iscsi</code>,
|
|
<code>logical</code>. This corresponds to the storage backend drivers
|
|
listed further along in this document.
|
|
The storage pool XML format is available <span class="since">since 0.4.1</span>
|
|
</p>
|
|
<h3><a name="StoragePoolFirst">General metadata</a></h3>
|
|
|
|
<pre>
|
|
<pool type="iscsi">
|
|
<name>virtimages</name>
|
|
<uuid>3e3fce45-4f53-4fa7-bb32-11f34168b82b</uuid>
|
|
<allocation>10000000</allocation>
|
|
<capacity>50000000</capacity>
|
|
<available>40000000</available>
|
|
...</pre>
|
|
|
|
<dl>
|
|
<dt><code>name</code></dt>
|
|
<dd>Providing a name for the pool which is unique to the host.
|
|
This is mandatory when defining a pool. <span class="since">Since 0.4.1</span></dd>
|
|
<dt><code>uuid</code></dt>
|
|
<dd>Providing an identifier for the pool which is globally unique.
|
|
This is optional when defining a pool, a UUID will be generated if
|
|
omitted. <span class="since">Since 0.4.1</span></dd>
|
|
<dt><code>allocation</code></dt>
|
|
<dd>Providing the total storage allocation for the pool. This may
|
|
be larger than the sum of the allocation of all volumes due to
|
|
metadata overhead. This value is in bytes. This is not applicable
|
|
when creating a pool. <span class="since">Since 0.4.1</span></dd>
|
|
<dt><code>capacity</code></dt>
|
|
<dd>Providing the total storage capacity for the pool. Due to
|
|
underlying device constraints it may not be possible to use the
|
|
full capacity for storage volumes. This value is in bytes. This
|
|
is not applicable when creating a pool. <span class="since">Since 0.4.1</span></dd>
|
|
<dt><code>available</code></dt>
|
|
<dd>Providing the free space available for allocating new volumes
|
|
in the pool. Due to underlying device constraints it may not be
|
|
possible to allocate the entire free space to a single volume.
|
|
This value is in bytes. This is not applicable when creating a
|
|
pool. <span class="since">Since 0.4.1</span></dd>
|
|
</dl>
|
|
|
|
<h3><a name="StoragePoolSource">Source elements</a></h3>
|
|
|
|
<p>
|
|
A single <code>source</code> element is contained within the top level
|
|
<code>pool</code> element. This tag is used to describe the source of
|
|
the storage pool. It can contain the following child elements:
|
|
</p>
|
|
|
|
<pre>
|
|
...
|
|
<source>
|
|
<host name="iscsi.example.com"/>
|
|
<device path="demo-target"/>
|
|
</source>
|
|
...</pre>
|
|
|
|
<dl>
|
|
<dt><code>device</code></dt>
|
|
<dd>Provides the source for pools backed by physical devices.
|
|
May be repeated multiple times depending on backend driver. Contains
|
|
a single attribute <code>path</code> which is the fully qualified
|
|
path to the block device node. <span class="since">Since 0.4.1</span></dd>
|
|
<dt><code>directory</code></dt>
|
|
<dd>Provides the source for pools backed by directories. May
|
|
only occur once. Contains a single attribute <code>path</code>
|
|
which is the fully qualified path to the block device node.
|
|
<span class="since">Since 0.4.1</span></dd>
|
|
<dt><code>adapter</code></dt>
|
|
<dd>Provides the source for pools backed by SCSI adapters. May
|
|
only occur once. Contains a single attribute <code>name</code>
|
|
which is the SCSI adapter name (ex. "host1").
|
|
<span class="since">Since 0.6.2</span></dd>
|
|
<dt><code>host</code></dt>
|
|
<dd>Provides the source for pools backed by storage from a
|
|
remote server. Will be used in combination with a <code>directory</code>
|
|
or <code>device</code> element. Contains an attribute <code>name</code>
|
|
which is the hostname or IP address of the server. May optionally
|
|
contain a <code>port</code> attribute for the protocol specific
|
|
port number. <span class="since">Since 0.4.1</span></dd>
|
|
<dt><code>name</code></dt>
|
|
<dd>Provides the source for pools backed by storage from a
|
|
named element (e.g., a logical volume group name).
|
|
remote server. Contains a string identifier.
|
|
<span class="since">Since 0.4.5</span></dd>
|
|
<dt><code>format</code></dt>
|
|
<dd>Provides information about the format of the pool. This
|
|
contains a single attribute <code>type</code> whose value is
|
|
backend specific. This is typically used to indicate filesystem
|
|
type, or network filesystem type, or partition table type, or
|
|
LVM metadata type. All drivers are required to have a default
|
|
value for this, so it is optional. <span class="since">Since 0.4.1</span></dd>
|
|
</dl>
|
|
|
|
<h3><a name="StoragePoolTarget">Target elements</a></h3>
|
|
|
|
<p>
|
|
A single <code>target</code> element is contained within the top level
|
|
<code>pool</code> element. This tag is used to describe the mapping of
|
|
the storage pool into the host filesystem. It can contain the following
|
|
child elements:
|
|
</p>
|
|
|
|
<pre>
|
|
...
|
|
<target>
|
|
<path>/dev/disk/by-path</path>
|
|
<permissions>
|
|
<owner>107</owner>
|
|
<group>107</group>
|
|
<mode>0744</mode>
|
|
<label>virt_image_t</label>
|
|
</permissions>
|
|
<encryption type='...'>
|
|
...
|
|
</encryption>
|
|
</target>
|
|
</pool></pre>
|
|
|
|
<dl>
|
|
<dt><code>path</code></dt>
|
|
<dd>Provides the location at which the pool will be mapped into
|
|
the local filesystem namespace. For a filesystem/directory based
|
|
pool it will be the name of the directory in which volumes will
|
|
be created. For device based pools it will be the name of the directory in which
|
|
devices nodes exist. For the latter <code>/dev/</code> may seem
|
|
like the logical choice, however, devices nodes there are not
|
|
guaranteed stable across reboots, since they are allocated on
|
|
demand. It is preferable to use a stable location such as one
|
|
of the <code>/dev/disk/by-{path,id,uuid,label</code> locations.
|
|
<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>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 be either a file or a device node.
|
|
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>
|
|
<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. <span class="since">Since 0.4.1</span></dd>
|
|
<dt><code>key</code></dt>
|
|
<dd>Providing an identifier for the volume which is globally unique.
|
|
This 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.<br/>
|
|
<br/>
|
|
By default this is specified in bytes, but an optional
|
|
<code>unit</code> can be specified to adjust the passed value.
|
|
Values can be: 'K' (kilobytes), 'M' (megabytes), 'G' (gigabytes),
|
|
'T' (terabytes), 'P' (petabytes), or 'E' (exabytes).
|
|
<span class="since">Since 0.4.1</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>
|
|
</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 type. 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 pool-specific docs for
|
|
the list of valid values. <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>
|
|
</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="demo-target"/>
|
|
</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>
|