reinstalling with existing lvm

[mike_d]

maybe this is easier than i thought, but i couldn't find any topics that delt with this. i have a gentoo system set up that the whole OS is installed on an old scsi drive. i also have a 4 ide drives in a LVM2 setup that contain a bunch of data. this weekend the scsi drive died (i have no backup of that drive - it's just the OS, no data), and i'll need to re-install gentoo on it. once i get everything installed, how do i go about telling the OS that i have 4 drives in a LVM already created?

thanks!
mike