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Utilizing LVM
The needs of your organization will change with time. While we as server 
administrators always do our best to configure resources with long-term growth 
in mind, budgets and changes in policy always seem to get in our way. LVM is 
something that I'm sure you'll come to appreciate. In fact, technologies such as 
LVM are those things that make Linux the champion when it comes to scalability 
and cloud deployments. With LVM, you are able to resize your filesystems online, 
without needing to reboot your server. LVM allows you to stop thinking of storage 
in terms of Linux, but instead to think of it in terms of scalability.
Take the following scenario for example. Say you have an application running on 
a virtualized production server, a server that's so important that downtime would 
cost your organization serious money. When the server was first set up, perhaps you 
gave the application's storage directory a 100 GB partition, thinking it would never 
need more than that. Now, with your business growing, it's not only using a lot of 
space—you're about to run out! What do you do? If the server was initially set up 
with LVM, you could add an additional storage volume, add it to your LVM pool, 
and grow your partition, all without rebooting your server! On the other hand, if 
you didn't use LVM, you're forced to find a maintenance window for your server 
and add more storage the old-fashioned way, which would include having it be 
inaccessible for a time.
It's for this reason that I must stress that you should always use LVM on storage 
volumes in virtual servers whenever possible. Let me repeat myself: you should 
always
 use LVM on storage volumes when you are setting up a virtual server! If you 
don't, this will eventually catch up with you when your available space starts to run 
out and you find yourself working over the weekend to add new disks. This will 
involve manually syncing data from one disk to another and then migrating your 
users to the new disk. This is not a fun experience, believe me. You might not think 
you'll be needing LVM right now, but you never know.
With physical servers, you can install additional hard drives and 
keep them on standby without utilizing them to still gain the 
benefit of growing your filesystem online, even though your server 
isn't virtual. In addition, if your server supports hot-plugging, 
you can still add additional volumes without powering the server 
down.

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Managing Storage Volumes