LVM (Logical Volume Management) – Combine Physical Drives and more!
LVM is a very cool volume management tool. It can be used for a variety of tasks and this guide explains all the things LVM can do. I also do an example video of combining physical hard drives using LVM.
Acronyms you must know!
PV – Physical Volume
VG – Volume Group
LV – Logical Volume
LVM Commands
LVM Layer 1 – Hard Drives, Partitions, and Physical Volumes
lvmdiskscan – system readout of volumes and partitions
pvdisplay – display detailed info on physical volumes
pvscan – display disks with physical volumes
pvcreate /dev/sda1 – create a physical volume from sda1
pvchange -x n /dev/sda1 – Disallow using a disk partition
pvresize /dev/sda1 – resize sda1 PV to use all of the partition
pvresize --setphysicalvolumesize 140G /dev/sda1 – resize sda1 to 140g
pvmove /dev/sda1 – can move data out of sda1 to other PVs in VG. Note: Free disk space equivalent to data moved is needed elsewhere.
pvremove /dev/sda1 – delete Physical volume
LVM Layer 2 – Volume Groups
vgcreate vg1 /dev/sda1 /dev/sdb1 – create a volume group from two drives
vgextend vg1 /dev/sdb1 – add PV to the volume group
vgdisplay vg1 – Display details on a volume group
vgscan – list volume groups
vgreduce vg1 /dev/sda1 – Removes the drive from vg1
Note: use pvmove /dev/sda1 before removing the drive from vg1
vgchange – you can activate/deactive and change perameteres
vgremove vg1 – Remove volume group vg1
vgsplit and vgmerge can split and merge volume groups
vgrename– renames a volume group
LVM Layer 3 – Logical Volumes and File Systems
lvcreate -L 10G vg1 – create a 10 GB logical volume on volume group vg1
lvchange and lvreduce are commands that typically aren’t used
lvrename– rename logical volume
lvremove – removes a logical volume
lvscan – shows logical volumes
lvdisplay – shows details on logical volumes
lvextend -l +100%FREE /dev/vg1/lv1– One of the most common commands used to extend logical volume lv1 that takes up ALL of the remaining free space on the volume group vg1.
resize2fs /dev/vg1/lv1 – resize the file system to the size of the logical volume lv1.
LVM conclusion
LVM is fantastic for managing a system, but remember that the more drives you make in a volume group that the likely it is to fail. Instead of having one point of failure you can open yourself up for multiple points when making a large system with multiple drives.