Configure LVM in RHEL6

LVM is a form of advanced partition management. The benefit to using LVM is ease of   management due to the way disks are set up.When you set up your system for the first time, you have a certain number of physical  disks . These physical disks are the base of the LVM structure and referred to as physical volumes. The next layer in the structure is volume groups, where physical volumes are combined into  a single pool of storage. The final layer in the structure is logical volumes, which are the actual partitions on the system.

There are many commands and management utilities for working with LVM. Here is an overview of them:

pvdisplay          Displays detailed information on physical volumes
vgdisplay          Displays detailed information on volume groups
lvdisplay           Displays detailed information on logical volumes

pvcreate           Creates a new physical volume
vgcreate           Creates a new volume group
lvcreate            Creates a new logical volume

vgextend           Extends an existing volume group
lvextend            Extends a logical volume
lvresize             Resizes a logical volume
lvreduce            Reduces a logical volume

Configuration steps
Step 1.
Install the required packages:
# yum install -y lvm*

Step 2.
To create physical partiion use the pvcreate command:
# pvcreate /dev/hdb4
# pvcreate /dev/hdb5

Step 3.
With the disk initialized, you can next create a volume group and add the physical disk to it.
To create the volume group, use the vgcreate command:
# vgcreate vg_name /dev/hdb4 /dev/hdb5

Step 4.
Now you can set up logical volumes that hold the partitions for the system. To create a logical volume,
Create a partition 3GB in size name as lvm_name
# lvcreate -L 3000 -n lvm_name vg_name

Step 5.
Verify that the logical volume was created successfully:
# lvdisplay vg_name
Step 6.
To extend or reduce a logical volume use the lvextend & lvreduce command.
 Add 2GB more to the lvm_name logical volume:
# lvextend -L +2000 /dev/vg_name/lvm_name

# lvreduce -L -2000 /dev/vg_name/lvm_name

Verify the change with the following command:
# lvdisplay vg_name


Removing LVM

To remove a logical volume, firstly umount LVM partition if mounted then use the lvremove command:
# lvremove /dev/vg_name/lvm_name



Use the vgremove command to remove the volume group:
# vgremove vg_name

 To Remove Physical Volume

#pvremove /dev/hdb4

Labels on physical volume “/dev/hdb4” successfully wiped