LVM is a Logical Volume Manager for the Linux operating system. There are now two version of LVM for Linux:
LVM 2 - The latest and greatest version of LVM for Linux.
LVM 2 is almost completely backward compatible with volumes created with LVM 1. The exception to this is snapshots (You must remove snapshot volumes before upgrading to LVM 2)
LVM 2 uses the device mapper kernel driver. Device mapper support is in the 2.6 kernel tree and there are patches available for current 2.4 kernels.
LVM 1 - The version that is in the 2.4 series kernel,
LVM 1 is a mature product that has been considered stable for a couple of years. The kernel driver for LVM 1 is included in the 2.4 series kernels, but this does not mean that your 2.4.x kernel is up to date with the latest version of LVM. Look at the README for the latest information about which kernels have the current code in them.