The MLN Project

Using LVM under MLN

LVM - logical volume management, is a dynamic way to create partitions - called volumes. In terms of virtualization, it is popular to use LVM volumes as harddisks for the VMs because of a improved disk performance compared to the default filesystem image files. This will work both for UML and Xen virtual machines.

Setting up LVM for MLN is not a very difficult task. First of all, you need to have the lvm tools installed, but they come with most of todays distributions already. The summary of this example, is that it will show you how to create a LVM volume group and how to make MLN place its filesystems there.

1. Assigning the partitions to use

First of all, you'll need one or more partitions. You can increase the size of the LVM volume group later with more partitions. If you want better performance and have several disks, you can create a software RAID first, and then use that for the volume group. Lets say you want to use partition /dev/sdb1:

pvcreate /dev/sdb1

2. Creating the volume group

Next, we create the actual LVM volume group. You can choose any name you want for it, but the default for MLN is "mln-images", and we will use that here:

vgcreate mln-images /dev/sdb1

3. Modifying /etc/mln/mln.conf

This is not strictly necessary if you called your volume group "mln-images". Make sure you have the following line in /etc/mln/mln.conf:

lvm_vg /dev/your-vg-name

4. Building a project with LVM

This is a very simple project, that will put the filesystem on on the LVM volume group:

global {

       project lvm-test

       }



host one {

     lvm

     term screen

}

Build this project, start it, and connect to the screen terminal: screen -r one.lvm-test. Also, you can check the presence of the LVM filesystem:

ls /dev/mln-images/one.lvm-test

.