migrate root fs to lvm

hi There,

rhel6 was built on standard disk partition instead of lvm and when we are trying to migrate we are facing issues.

We have migrated to new lvm disk and able to boot with two boot envs if two disks are attached, but when we detach old disk we are not able to boot the server.Can you please help us on this?
Our server was built on VMWARE 5.x version