What does pvmove do?

Question

man pvmove says

pvmove moves the allocated physical extents (PEs) on a source PV to one or more destination PVs. You can optionally specify a source LV in which case only extents used by that LV will be moved to free (or specified) extents on the destination PV. If no destination PV is specified, the normal allocation rules for the VG are used.

What does "moves the allocated physical extents (PEs) on a source PV to one or more destination PVs" mean?

What is the difference between pvmove and pvresize? Does pvmove shrink a PV and then use the freed up space to enlarge another PV?

There is a device ( a disk or partition) underlying each PV. Does pvmove work along with another command which resizes the underlying devices of the two PVs involved?

Thanks.

Answer 1

What does "moves the allocated physical extents (PEs) on a source PV to one or more destination PVs" mean?

It means what it says. The extents (blocks of data) in one PV are moved to another one. For example, if you have two PVs /dev/sda1 and /dev/sdb1 for a VG you can move the extents from /dev/sda1 to /dev/sdb1). Assuming you had enough space on /dev/sdb1 this would allow you to remove /dev/sda1 from the VG, possibly even removing the entire /dev/sda from the system.

What is the difference between pvmove and pvresize? Does pvmove shrink a PV and then use the freed up space to enlarge another PV

pvmove moves data from one physical device in a VG to another. pvresize changes the size used by a PV. An example from the man page suggests this might be done after changing the size of a partition with fdisk.

Does pvmove work along with another command which resizes the underlying devices of the two PVs involved?

pvresize resizes a PV. pvmove moves the extents (data blocks) from one PV to another.