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5.4.8. Merging Snapshot Volumes
As of the Red Hat Enterprise Linux 6 release, you can use the
--mergeoption of the
lvconvertcommand to merge a snapshot into its origin volume. If both the origin and snapshot volume are not open, the merge will start immediately. Otherwise, the merge will start the first time either the origin or snapshot are activated and both are closed. Merging a snapshot into an origin that cannot be closed, for example a root file system, is deferred until the next time the origin volume is activated. When merging starts, the resulting logical volume will have the origin’s name, minor number and UUID. While the merge is in progress, reads or writes to the origin appear as they were directed to the snapshot being merged. When the merge finishes, the merged snapshot is removed.
The following command merges snapshot volume
vg00/lvol1_snapinto its origin.
lvconvert --merge vg00/lvol1_snap
You can specify multiple snapshots on the command line, or you can use LVM object tags to specify that multiple snapshots be merged to their respective origins. In the following example, logical volumes
vg00/lvol3are all tagged with the tag
@some_tag. The following command merges the snapshot logical volumes for all three volumes serially:
vg00/lvol3. If the
--backgroundoption were used, all snapshot logical volume merges would start in parallel.
lvconvert --merge @some_tag
For information on tagging LVM objects, see Appendix D, LVM Object Tags. For further information on the
lvconvert --mergecommand, see the
lvconvert(8) man page.