hesela.devVolume group (LVM)
In Linux LVM, a volume group is a named collection of physical volumes whose extents provide allocation space for logical volumes.
A VG can contain one PV or several. Physical-extent size and allocation policy govern allocation within the group. Grouping PVs does not itself add application-data redundancy: protection depends on the LV layout and its backing devices. [1] [2]
Adding a PV with vgextend increases space available for LV allocation. It does not enlarge every existing LV or the filesystems using them. Those are separate resizing operations. [3]
VG free extents and unused thin-pool capacity are different resources. A thin pool has allocated data and metadata components; Data% and Meta% describe usage within them. Growing those components requires free VG extents and a successful extension, not merely the presence of space elsewhere in the group. [4]
A free-extent total does not guarantee a usable placement. The normal policy avoids parallel stripes on the same PV; contiguous allocation also constrains adjacency. A request can therefore lack eligible extents despite free space in the VG. This is not a recommendation to weaken allocation policy. [1]
Relations
Limitations
- A VG configuration backup does not contain the data stored in its logical volumes. [5]
Citations
- LVM2 lvm(8): PV/VG/LV hierarchy and allocation policies
- LVM2 vgcreate(8): physical-extent size and VG creation
- LVM2 vgextend(8): adding PVs increases available LV-allocation space
- LVM2 lvmthin(7): pool usage counters and extension requirements
- LVM2 vgcfgbackup(8): configuration backup excludes LV contents