libvirt/docs/schemas/domainsnapshot.rng
Eric Blake 4201a7ea1c snapshot: new XML for external system checkpoint
Each <domainsnapshot> can now contain an optional <memory>
element that describes how the VM state was handled, similar
to disk snapshots.  The new element will always appear in
output; for back-compat, an input that lacks the element will
assume 'no' or 'internal' according to the domain state.

Along with this change, it is now possible to pass <disks> in
the XML for an offline snapshot; this also needs to be wired up
in a future patch, to make it possible to choose internal vs.
external on a per-disk basis for each disk in an offline domain.
At that point, using the --disk-only flag for an offline domain
will be able to work.

For some examples below, remember that qemu supports the
following snapshot actions:

qemu-img: offline external and internal disk
savevm: online internal VM and disk
migrate: online external VM
transaction: online external disk

=====
<domainsnapshot>
  <memory snapshot='no'/>
  ...
</domainsnapshot>

implies that there is no VM state saved (mandatory for
offline and disk-only snapshots, not possible otherwise);
using qemu-img for offline domains and transaction for online.

=====
<domainsnapshot>
  <memory snapshot='internal'/>
  ...
</domainsnapshot>

state is saved inside one of the disks (as in qemu's 'savevm'
system checkpoint implementation).  If needed in the future,
we can also add an attribute pointing out _which_ disk saved
the internal state; maybe disk='vda'.

=====
<domainsnapshot>
  <memory snapshot='external' file='/path/to/state'/>
  ...
</domainsnapshot>

This is not wired up yet, but future patches will allow this to
control a combination of 'virsh save /path/to/state' plus disk
snapshots from the same point in time.

=====

So for 1.0.1 (and later, as needed), I plan to implement this table
of combinations, with '*' designating new code and '+' designating
existing code reached through new combinations of xml and/or the
existing DISK_ONLY flag:

domain  memory  disk   disk-only | result
-----------------------------------------
offline omit    omit   any       | memory=no disk=int, via qemu-img
offline no      omit   any       |+memory=no disk=int, via qemu-img
offline omit/no no     any       | invalid combination (nothing to snapshot)
offline omit/no int    any       |+memory=no disk=int, via qemu-img
offline omit/no ext    any       |*memory=no disk=ext, via qemu-img
offline int/ext any    any       | invalid combination (no memory to save)
online  omit    omit   off       | memory=int disk=int, via savevm
online  omit    omit   on        | memory=no disk=default, via transaction
online  omit    no/ext off       | unsupported for now
online  omit    no     on        | invalid combination (nothing to snapshot)
online  omit    ext    on        | memory=no disk=ext, via transaction
online  omit    int    off       |+memory=int disk=int, via savevm
online  omit    int    on        | unsupported for now
online  no      omit   any       |+memory=no disk=default, via transaction
online  no      no     any       | invalid combination (nothing to snapshot)
online  no      int    any       | unsupported for now
online  no      ext    any       |+memory=no disk=ext, via transaction
online  int/ext any    on        | invalid combination (disk-only vs. memory)
online  int     omit   off       |+memory=int disk=int, via savevm
online  int     no/ext off       | unsupported for now
online  int     int    off       |+memory=int disk=int, via savevm
online  ext     omit   off       |*memory=ext disk=default, via migrate+trans
online  ext     no     off       |+memory=ext disk=no, via migrate
online  ext     int    off       | unsupported for now
online  ext     ext    off       |*memory=ext disk=ext, via migrate+transaction

* docs/schemas/domainsnapshot.rng (memory): New RNG element.
* docs/formatsnapshot.html.in: Document it.
* src/conf/snapshot_conf.h (virDomainSnapshotDef): New fields.
* src/conf/domain_conf.c (virDomainSnapshotDefFree)
(virDomainSnapshotDefParseString, virDomainSnapshotDefFormat):
Manage new fields.
* tests/domainsnapshotxml2xmltest.c: New test.
* tests/domainsnapshotxml2xmlin/*.xml: Update existing tests.
* tests/domainsnapshotxml2xmlout/*.xml: Likewise.
2012-11-02 09:56:23 -06:00

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XML

<?xml version="1.0"?>
<!-- A Relax NG schema for the libvirt domain snapshot properties XML format -->
<grammar xmlns="http://relaxng.org/ns/structure/1.0">
<start>
<ref name='domainsnapshot'/>
</start>
<include href='domaincommon.rng'/>
<define name='domainsnapshot'>
<element name='domainsnapshot'>
<interleave>
<optional>
<element name='name'>
<text/>
</element>
</optional>
<optional>
<element name='description'>
<text/>
</element>
</optional>
<optional>
<element name='state'>
<ref name='state'/>
</element>
</optional>
<optional>
<element name='creationTime'>
<text/>
</element>
</optional>
<optional>
<element name='memory'>
<choice>
<attribute name='snapshot'>
<choice>
<value>no</value>
<value>internal</value>
</choice>
</attribute>
<group>
<optional>
<attribute name='snapshot'>
<value>external</value>
</attribute>
</optional>
<attribute name='file'>
<ref name='absFilePath'/>
</attribute>
</group>
</choice>
<empty/>
</element>
</optional>
<optional>
<element name='disks'>
<zeroOrMore>
<ref name='disksnapshot'/>
</zeroOrMore>
</element>
</optional>
<optional>
<element name='active'>
<choice>
<value>0</value>
<value>1</value>
</choice>
</element>
</optional>
<optional>
<choice>
<element name='domain'>
<element name='uuid'>
<ref name="UUID"/>
</element>
</element>
<ref name='domain'/>
</choice>
</optional>
<optional>
<element name='parent'>
<element name='name'>
<text/>
</element>
</element>
</optional>
</interleave>
</element>
</define>
<define name='state'>
<choice>
<value>nostate</value>
<value>running</value>
<value>blocked</value>
<value>paused</value>
<value>shutdown</value>
<value>shutoff</value>
<value>crashed</value>
<value>disk-snapshot</value>
</choice>
</define>
<define name='disksnapshot'>
<element name='disk'>
<attribute name='name'>
<choice>
<ref name='diskTarget'/>
<ref name='absFilePath'/>
</choice>
</attribute>
<choice>
<attribute name='snapshot'>
<value>no</value>
</attribute>
<attribute name='snapshot'>
<value>internal</value>
</attribute>
<group>
<optional>
<attribute name='snapshot'>
<value>external</value>
</attribute>
</optional>
<interleave>
<optional>
<element name='driver'>
<optional>
<attribute name='type'>
<ref name='diskFormat'/>
</attribute>
</optional>
<empty/>
</element>
</optional>
<optional>
<element name='source'>
<optional>
<attribute name='file'>
<ref name='absFilePath'/>
</attribute>
</optional>
<empty/>
</element>
</optional>
</interleave>
</group>
</choice>
</element>
</define>
</grammar>