3:12 a.m.
Applications based on libvirt such as OpenStack need some public APIs
about export/import of external snapshot during daily backup, snapshot
recovery or system migration. virDomainSnapshotDiskExport,
virDomainSnapshotVmstateExport and virDomainSnapshotImport are designed
to satisfy such requirement.
@flags: virDomainSnapshotExportImportFlags include,
DATA_FULL: all data snapshot
DATA_DELTA: delta data only
/**
* virDomainSnapshotDiskExport
* @domain: the domain object to be exported snapshot
* @id: top Overlays which to be exported
* @base_id: RootBase of snapshot to be exported
* @disk: block device of domain
* @export_path: path of snapshots export
* @flags: bitwise-OR of virDomainSnapshotExportImportFlags
*
* Import snapshot disk data to the pointed path.
*
* If @flags includes DATA_FULL, full backup snapshot will be exported.
*
* If @flags includes DATA_DELTA, incremental backup snapshot will be
* exported.
*
* DATA_FULL and DATA_DELTA should not appear at the same time
*
* Returns 0 on success, or -1 on error
*/
int virDomainSnapshotDiskExport(virDomain *domain,
virSnapshotId *id,
virSnapshotId *base_id,
virDevice *disk,
char *export_path,
unsigned int flags)
Usage: export external snapshot disk file from virtual machine to the
target path.
/**
* virDomainSnapshotVmstateExport
* @domain: the domain object to be exported snapshot
* @id: top Overlays which to be exported
* @export_path: path of snapshots export
* @flags: not used yet, so callers should always pass 0
*
* Import snapshot vmstate data to the pointed path.
*
* If @flags includes DATA_FULL, full backup snapshot will be exported.
*
* If @flags includes DATA_DELTA, incremental backup snapshot will be
* exported.
*
* DATA_FULL and DATA_DELTA should not appear at the same time
*
* Returns 0 on success, or -1 on error
*/
int virDomainSnapshotVmstateExport(virDomain *domain,
virSnapshotId *id,
char *export_path,
unsigned int flags)
Usage: dump vmstate file of snapshot and copy it to the target path.
/**
* virDomainSnapshotImport
* @domain: the domain object to be exported snapshot
* @xmlDesc: string containing an XML description of the domain
* @flags: bitwise-OR of virDomainSnapshotExportImportFlags
*
* Import snapshot data to the pointed path.
*
* If @flags includes DATA_FULL, full backup snapshot will be exported.
*
* If @flags includes DATA_DELTA, incremental backup snapshot will be
* exported.
*
* DATA_FULL and DATA_DELTA should not appear at the same time
*
* Returns 0 on success, or -1 on error
*/
int virDomainSnapshotImport(virDomain *domain,
const char *xmlDesc,
unsigned int flags)
Usage: import .xml file of external snapshot and use it for recovering
a virtual machine.
Usecase:
If users want to finish daily backup&recovery work by above APIs,
the process should be,
1. call virDomainSnapshotDiskExport() to export pointed snapshot
disk files to the traget path.
------------------- ---------------------
| host A | | host B |
| --------------- | | ----------------- |
| | dom1 | | snapshot disk files | | backup folder | |
| | base.img----------------------------------->base.img | |
| | snap1.qcow2-------------------------------->snap1.qcow2 | |
| | snap2.qcow2-------------------------------->snap2.qcow2 | |
| --------------- | | ----------------- |
------------------- ---------------------
virDomainSnapshotDiskSnapshot()
2. call virDomainSnapshotVmstateExport() to export vmstate data
file to the target path.
--------------- ---------------------
| host A | | host B |
| ----------- | | ----------------- |
| | dom1 | | vmstate data files | | backup folder | |
| | dumpxml-------------------------------->vmstate.xml | |
| ----------- | | ----------------- |
--------------- ---------------------
virDomainSnapshotVmstateSnapshot()
3. when some error occured, or guest copy/migration, users copy
snapshot disk files from host B to the target host and edit <source
file> field of <disk> tag. Then users call virDomainSnapshotImport
to recovery domain to the snapshot.
a. copy snapshot disk files to the target host:
------------------------------- ---------------------
| host A | snapshot | host B |
| --------------------------- | disk | ----------------- |
| | /var/lib/libvirt/images | | files | | backup folder | |
| | base.img<-----------------------------------base.img | |
| | snap1.qcow2<--------------------------------snap1.qcow2 | |
| | snap2.qcow2<--------------------------------snap2.qcow2 | |
| --------------------------- | | ----------------- |
------------------------------- ---------------------
snapshot disk files transfer
b. import vmstate data to recovery snapshot:
---------------------
------------------- | host B |
| host A | | ----------------- |
| --------------- | vmstate data | | backup folder | |
| | dom1<-------------------------------vmstate.xml | |
| | base.img | | | ----------------- |
| | snap1.qcow2 | | ---------------------
| | snap2.qcow2 | |
| --------------- |
-------------------
virDomainSnapshotImport()