Creating an LVM group

Question

I have rented a dedicated server with two 500gb hardisks running centos 6.

On this server there are 3 partitions.

1. boot
2. root 50gb
3. swap 50gb
4. empty 400gb

Now I want to create a logical volume group spanning the empty 400gb on the first disk and merginging it with the empty 400gb on the second disk.

I've read tutorial after tutorial but I cannot understand how to accomplish this task. I just want to merge the empty partition with the empty disk.

Can someone please suggest how may I accomplish this, or if it is at all possible?

Answer 1

It is possible to do this. There are 3 parts to LVM -

• The Physical Volume
• The Volume Group
• Logical Volumes

So the way I would do this is to create a partition on the second disk (you don't need to do this, but its the "correct" way to do it)

First instruct the Operating system that you have 2 Physical Volumes you wish to assign to LVM - you do this by running the following command for each of the 2 partitions

pvcreate /dev/sdXX     

The second step is to assign both physical volumes into 1 volume group -

vgcreate vgname /dev/sdXX /dev/sdXX

The third step is to create a logical volume

lvcreate -n NewPartitionName vg -L 899G

In this example I've created an 899 gig block device which will be called /dev/vgname/NewPartitionName. Depending on your needs, seriously consider starting off only using, say 800 Gigs of space, leaving the last 99 gigs free - this will give you freedom to create additional volumes - including snapshots, which can be useful. You can always expand the current volume later (even when the filesystem is in use). Its is easier to make a volume bigger then smaller.

At this stage you are ready to add your filesystem. Not sure if you need help here, but you could use a command mkfs.ext4 /dev/vgname/NewPartitionName to format the partition. You can then add it to your fstab file if you want it to be automatically mounted.