-
Notifications
You must be signed in to change notification settings - Fork 2
Expand file tree
/
Copy pathformatstorage.html.in
More file actions
436 lines (400 loc) · 19.8 KB
/
formatstorage.html.in
File metadata and controls
436 lines (400 loc) · 19.8 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
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
<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 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"/>
<vendor name="Acme"/>
<product name="model"/>
</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>
<dt><code>vendor</code></dt>
<dd>Provides optional information about the vendor of the
storage device. This contains a single
attribute <code>name</code> whose value is backend
specific. <span class="since">Since 0.8.4</span></dd>
<dt><code>product</code></dt>
<dd>Provides an optional product name of the storage device.
This contains a single attribute <code>name</code> whose value
is backend specific. <span class="since">Since 0.8.4</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>
<timestamps>
<atime>1341933637.273190990</atime>
<mtime>1341930622.047245868</mtime>
<ctime>1341930622.047245868</ctime>
</timestamps>
<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>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 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 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>
</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>