Originally Posted by mmhs
my question is where or when LVM is not benefit or not recommended
Well, the only times I would "not" recommend LVM would be the following;
When a person is first starting to use Linux.
If they are interested in the "System Administration" side of things, but don't yet have a strong enough *NIX background, then I would not recommend they start down the LVM or LVM+RAID path just yet.
When the system only has one hard drive, dedicated to that one Operating System.
Such is the case with Laptops that are not dual-booting with Windows.
If it's a Virtual Machine that's using virtual disks.
For example, with VMware, I would just create a few small virtual disk rather than committing one large virtual disk to the Virtual Machine, then trying to layer LVM on top of it.
However, bear in mind that LVM (especially LVM+RAID) is *great* when you have more than one physical hard disk of roughly the same size, and you want redundancy along easy filesystem management.