Logical Volume Management (LVM) on RHEL

Overview

Logical Volume Management (LVM) provides a flexible way to manage disk storage in Linux by abstracting physical storage devices into logical volumes that can be resized or moved without downtime. RHEL uses the lvm2 package for LVM management.

LVM Components

  • Physical Volume (PV): A storage device or partition initialized for LVM.
  • Volume Group (VG): A collection of physical volumes that act as a single storage pool.
  • Logical Volume (LV): The virtual partition created from a volume group; can host a filesystem.
  • Physical Extents (PE): The smallest allocatable unit on a physical volume.

LVM Commands Summary

1. Managing Physical Volumes 

# Create a physical volume
pvcreate /dev/sdb

# Display physical volumes
pvdisplay
pvs

# Remove a physical volume from LVM
pvremove /dev/sdb

2. Managing Volume Groups 

# Create a volume group
vgcreate vg_data /dev/sdb /dev/sdc

# Display volume groups
vgdisplay
vgs

# Extend a volume group
vgextend vg_data /dev/sdd

# Reduce a volume group (ensure LV is moved or removed first)
vgreduce vg_data /dev/sdb

# Remove a volume group
vgremove vg_data

3. Managing Logical Volumes 

# Create a logical volume (size 20G)
lvcreate -L 20G -n lv_storage vg_data

# Create a logical volume using all remaining space
lvcreate -l 100%FREE -n lv_backup vg_data

# Display logical volumes
lvdisplay
lvs

# Remove a logical volume
lvremove /dev/vg_data/lv_storage

Filesystem Management 

# Create a filesystem on a logical volume
mkfs.xfs /dev/vg_data/lv_storage

# Mount the logical volume
mkdir /mnt/storage
mount /dev/vg_data/lv_storage /mnt/storage

# Persist mount across reboots
echo '/dev/vg_data/lv_storage /mnt/storage xfs defaults 0 0' >> /etc/fstab

Resizing Logical Volumes

Extend a Logical Volume 

# Extend LV by size
lvextend -L +10G /dev/vg_data/lv_storage

# Extend to use all free space
lvextend -l +100%FREE /dev/vg_data/lv_storage

# Resize filesystem (XFS)
xfs_growfs /mnt/storage

# Resize filesystem (EXT4)
resize2fs /dev/vg_data/lv_storage

Reduce a Logical Volume (EXT4 only) 

# Unmount first
umount /mnt/storage

# Run filesystem check
e2fsck -f /dev/vg_data/lv_storage

# Resize filesystem smaller than LV
resize2fs /dev/vg_data/lv_storage 10G

# Shrink logical volume
lvreduce -L 10G /dev/vg_data/lv_storage

# Mount again
mount /mnt/storage

LVM Snapshots 

# Create a snapshot (5G size)
lvcreate -L 5G -s -n lv_storage_snap /dev/vg_data/lv_storage

# List snapshots
lvs

# Merge snapshot back
lvconvert --merge /dev/vg_data/lv_storage_snap

LVM Thin Provisioning 

# Create thin pool
lvcreate --type thin-pool -L 100G -n thinpool vg_data

# Create thin volume
lvcreate -V 20G --thinpool thinpool -n lv_thin1 vg_data

# Display thin volumes
lvs -a

LVM Maintenance and Troubleshooting

Display LVM Status 

lvs
vgs
pvs

Remove Missing Physical Volumes 

vgreduce --removemissing vg_data

Repair Volume Group Metadata 

vgcfgrestore vg_data

Check Volume Group Consistency 

vgck vg_data

Configuration Files and Metadata

  • /etc/lvm/lvm.conf: Main LVM configuration file.
  • /etc/lvm/archive/: Stores metadata backups during LVM operations.
  • /etc/lvm/backup/: Manual and automatic volume group backups.

Best Practices

  • Always ensure backups before resizing or removing volumes.
  • Use vgcfgbackup before any major LVM operation.
  • Prefer XFS for large and growing filesystems (supports only growing, not shrinking).
  • Regularly monitor free space with lvs and vgs.
  • Use descriptive names for LVs and VGs to simplify management.

Example Workflow 

# Step 1: Create PVs
pvcreate /dev/sdb /dev/sdc

# Step 2: Create VG
vgcreate vg_storage /dev/sdb /dev/sdc

# Step 3: Create LV
lvcreate -L 50G -n lv_data vg_storage

# Step 4: Format and mount
mkfs.xfs /dev/vg_storage/lv_data
mkdir /mnt/data
mount /dev/vg_storage/lv_data /mnt/data

# Step 5: Extend LV when needed
lvextend -l +100%FREE /dev/vg_storage/lv_data
xfs_growfs /mnt/data

References