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94 lines
3.4 KiB
Plaintext
94 lines
3.4 KiB
Plaintext
.SH NOTES
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pvmove works as follows:
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1. A temporary 'pvmove' LV is created to store details of all the data
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movements required.
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2. Every LV in the VG is searched for contiguous data that need moving
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according to the command line arguments.
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For each piece of data found, a new segment is added to the end of the
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pvmove LV.
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This segment takes the form of a temporary mirror to copy the data
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from the original location to a newly allocated location.
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The original LV is updated to use the new temporary mirror segment
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in the pvmove LV instead of accessing the data directly.
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3. The VG metadata is updated on disk.
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4. The first segment of the pvmove LV is activated and starts to mirror
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the first part of the data. Only one segment is mirrored at once as this
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is usually more efficient.
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5. A daemon repeatedly checks progress at the specified time interval.
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When it detects that the first temporary mirror is in sync, it breaks that
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mirror so that only the new location for that data gets used and writes a
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checkpoint into the VG metadata on disk. Then it activates the mirror for
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the next segment of the pvmove LV.
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6. When there are no more segments left to be mirrored, the temporary LV
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is removed and the VG metadata is updated so that the LVs reflect the new
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data locations.
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Note that this new process cannot support the original LVM1
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type of on-disk metadata. Metadata can be converted using
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\fBvgconvert\fP(8).
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If the \fB\-\-atomic\fP option is used, a slightly different approach is
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used for the move. Again, a temporary 'pvmove' LV is created to store the
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details of all the data movements required. This temporary LV contains
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all the segments of the various LVs that need to be moved. However, in
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this case, an identical LV is allocated that contains the same number of
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segments and a mirror is created to copy the contents from the first
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temporary LV to the second. After a complete copy is made, the temporary
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LVs are removed, leaving behind the segments on the destination PV. If an
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abort is issued during the move, all LVs being moved will remain on the
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source PV.
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.SH EXAMPLES
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Move all physical extents that are used by simple LVs on the specified PV to
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free physical extents elsewhere in the VG.
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.br
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.B pvmove /dev/sdb1
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Use a specific destination PV when moving physical extents.
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.br
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.B pvmove /dev/sdb1 /dev/sdc1
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Move extents belonging to a single LV.
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.br
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.B pvmove \-n lvol1 /dev/sdb1 /dev/sdc1
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Rather than moving the contents of an entire device, it is possible to
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move a range of physical extents, for example numbers 1000 to 1999
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inclusive on the specified PV.
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.br
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.B pvmove /dev/sdb1:1000\-1999
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A range of physical extents to move can be specified as start+length. For
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example, starting from PE 1000. (Counting starts from 0, so this refers to the
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1001st to the 2000th PE inclusive.)
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.br
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.B pvmove /dev/sdb1:1000+1000
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Move a range of physical extents to a specific PV (which must have
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sufficient free extents).
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.br
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.B pvmove /dev/sdb1:1000\-1999 /dev/sdc1
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Move a range of physical extents to specific new extents on a new PV.
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.br
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.B pvmove /dev/sdb1:1000\-1999 /dev/sdc1:0\-999
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If the source and destination are on the same disk, the
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\fBanywhere\fP allocation policy is needed.
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.br
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.B pvmove \-\-alloc anywhere /dev/sdb1:1000\-1999 /dev/sdb1:0\-999
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The part of a specific LV present within in a range of physical
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extents can also be picked out and moved.
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.br
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.B pvmove \-n lvol1 /dev/sdb1:1000\-1999 /dev/sdc1
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