Section: Maintenance Commands (8)
Updated: LVM TOOLS (2) (2014-09-01)
pvmove [--abort] [--alloc AllocationPolicy] [--atomic] [-b|--background] [--commandprofile ProfileName] [-d|--debug] [-h|--help] [-i|--interval Seconds] [--noudevsync] [-v|--verbose] [-n|--name LogicalVolume] [SourcePhysicalVolume[:PE[-PE]...] [DestinationPhysicalVolume[:PE[-PE]...]...]]
pvmove allows you to move the allocated physical extents (PEs) on SourcePhysicalVolume to one or more other physical volumes (PVs). You can optionally specify a source LogicalVolume in which case only extents used by that LV will be moved to free (or specified) extents on DestinationPhysicalVolume(s). If no DestinationPhysicalVolume is specified, the normal allocation rules for the Volume Group are used.
If pvmove gets interrupted for any reason (e.g. the machine crashes) then run pvmove again without any PhysicalVolume arguments to restart any moves that were in progress from the last checkpoint. Alternatively use pvmove --abort at any time to abort. The resulting location of logical volumes after an abort is issued depends on whether the --atomic option was used when starting the pvmove process.
You can run more than one pvmove at once provided they are moving data off different SourcePhysicalVolumes, but additional pvmoves will ignore any Logical Volumes already in the process of being changed, so some data might not get moved.
pvmove works as follows:
1. A temporary 'pvmove' Logical Volume is created to store details of all the data movements required.
2. Every Logical Volume in the Volume Group is searched for contiguous data that need moving according to the command line arguments. For each piece of data found, a new segment is added to the end of the pvmove LV. This segment takes the form of a temporary mirror to copy the data from the original location to a newly-allocated location. The original LV is updated to use the new temporary mirror segment in the pvmove LV instead of accessing the data directly.
3. The Volume Group metadata is updated on disk.
4. The first segment of the pvmove Logical Volume is activated and starts to mirror the first part of the data. Only one segment is mirrored at once as this is usually more efficient.
5. A daemon repeatedly checks progress at the specified time interval. When it detects that the first temporary mirror is in-sync, it breaks that mirror so that only the new location for that data gets used and writes a checkpoint into the Volume Group metadata on disk. Then it activates the mirror for the next segment of the pvmove LV.
6. When there are no more segments left to be mirrored, the temporary Logical Volume is removed and the Volume Group metadata is updated so that the Logical Volumes reflect the new data locations.
If the --atomic option is used, a slightly different approach is used for the move. Again, a temporary 'pvmove' logical volume is created to store the details of all the data movements required. This temporary LV contains all the segments of the various LVs that need to be moved. However this time, an identical logical volume is allocated that contains the same number of segments and a mirror is created to copy the contents from the first temporary LV to the second. When a complete copy is accomplished, the temporary logical volumes are removed, leaving behind the segments on the destination physical volume. If an abort is issued during the move, all logical volumes being moved will remain on the source physical volume.
To move all Physical Extents that are used by simple Logical Volumes on /dev/sdb1 to free Physical Extents elsewhere in the Volume Group use:
Additionally, a specific destination device /dev/sdc1 can be specified like this:
pvmove /dev/sdb1 /dev/sdc1
To perform the action only on extents belonging to the single Logical Volume lvol1 do this:
pvmove -n lvol1 /dev/sdb1 /dev/sdc1
Rather than moving the contents of the entire device, it is possible to move a range of Physical Extents - for example numbers 1000 to 1999 inclusive on /dev/sdb1 - like this:
A range can also be specified as start+length, so
also refers to 1000 Physical Extents starting from Physical Extent number 1000. (Counting starts from 0, so this refers to the 1001st to the 2000th inclusive.)
To move a range of Physical Extents to a specific location (which must have sufficient free extents) use the form:
pvmove /dev/sdb1:1000-1999 /dev/sdc1
pvmove /dev/sdb1:1000-1999 /dev/sdc1:0-999
If the source and destination are on the same disk, the anywhere allocation policy would be needed, like this:
pvmove --alloc anywhere /dev/sdb1:1000-1999 /dev/sdb1:0-999
The part of a specific Logical Volume present within in a range of Physical Extents can also be picked out and moved, like this:
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