Mastering LVM: Physical Volumes, Volume Groups, and Advanced Operations

Running out of space on your Linux VM? No problem—LVM (Logical Volume Manager) and VMware vSphere make disk resizing straightforward. In this post, I'll walk you through the process of resizing LVM-managed disks, focusing on adding capacity to an existing disk in a vSphere environment.

Why Use an Unpartitioned Disk in LVM?

When managing storage with LVM, you have the flexibility of adding either a partition or an entire disk to a volume group (VG). Adding an unpartitioned disk can make things simpler.

Pros:

• Simplicity: No partition management means fewer steps
• Full Disk Utilization: No wasted space
• Efficiency: Adding capacity is much faster

Cons:

• Portability: Moving a raw disk might be tricky
• Compatibility: Backup tools often expect partition tables

Step-by-Step Guide to Resizing an LVM Disk in vSphere

Step 1: Resize the Disk in vSphere

1. Log in to vSphere client
2. Edit VM settings and increase disk size
3. Save changes

Step 2: Rescan the Disk in the VM

echo 1 > /sys/class/scsi_device/0:0:0:0/device/rescan

Step 3: Verify the Disk Size

lsblk

Step 4: Extend the Physical Volume

pvcreate /dev/sdb

Step 5: Add the PV to a Volume Group

vgextend <vg_name> /dev/sdb

Step 6: Verify and Expand

vgdisplay
lvresize -r -L +100G /dev/my_volume_group/my_logical_volume

Migrating Data Between Physical Volumes

Use pvmove to migrate data:

pvmove /dev/sdb /dev/sdc
vgreduce my_volume_group /dev/sdb
pvremove /dev/sdb

Backing Up Volume Group Configuration

vgcfgbackup my_volume_group
vgcfgrestore my_volume_group

Moving LVM PVs Between Machines

umount /mnt/my_logical_volume
vgchange -an my_volume_group
vgexport my_volume_group
# Move LUNs to destination
vgimport my_volume_group
vgchange -ay my_volume_group
mount /dev/my_volume_group/my_logical_volume /mnt/my_logical_volume

Using vgimportclone for Cloned VGs

vgimportclone -n new_volume_group_name /dev/sdX

Splitting a Volume Group

vgsplit my_volume_group new_volume_group lv_name1 lv_name2

Checking VG Metadata

vgck my_volume_group

Conclusion

Resizing LVM disks in VMware vSphere is straightforward. Whether using entire unpartitioned disks or partitions, each approach has advantages. LVM provides powerful tools for migrating data, backing up configurations, and moving storage between machines.