EMC PowerPath creates a new device name that represents the active path for each LUN presented by an EMC SAN to a server, or group of servers. The new devices are named /dev/emcpowera, /dev/emcpowerb, etc. However, PowerPath does not hide the original device names (/dev/sda, /dev/sdb, /dev/sdc, etc.). These /dev/sd* devices are treated by the server as if they were all unique devices, when in reality, they are just duplicate paths to the same devices presented by PowerPath. Novell Linux Volume Manager (NLVM) gets confused when it sees two devices that have duplicate pools. In reality, they are not duplicate pools, just duplicate paths to the same pool.