LVM is good because if you need more space on an LVM, you just add a drive to the LVM. LVM can be any combination of drives, even spanning machines, or ATA over ethernet. You could add a flash drive to a LVM. I don't believe optical drives work with LVM, but they might.

LVM has special tools you need to do simple operations. Once a person learns to use the tools, LVM is a piece of cake. But in this instance it can be a pain. Once a LVM is made, it isn't meant to be pulled apart in pieces, and mixed and matched on another LVM.

For most users discrete file systems are more flexible. But if someone is running an enterprise system, with no idea of how much storage space might be needed in the future, or if storage needs change wildy, LVM makes sense.

For instance, you want to make a storage device out of 3 raid arrays, with the option to add more. You just make a LVM out of the 3 external arrays. In the future you can add more arrays as needed.

What I don't like is that some distros make LVM the install default. Most people cannot benefit from LVM, so this default just drives support calls. That gets more people to pay for support, but it's really just a pain for everyone.

Thanks for the great information and all of your help here. You guys are the reason I joined this site.