This is how the EVMS and LVM2 interact with the Device mapper . EVMS(Enterprise. Vol Mgmt System) and the LVM2( an extension to Logical Vol Mgmt System (LVM) for 2.4) are user interfaces to interact with the kernel on logical device mgmt.
Basic SCSI terminologies around multipathing:
Physicalpath -> Unique combination of a SCSIinitiator and a SCSItarget,
Device -> SCSI Logicalunit ,
Path -> Logical Connection along a physical path to a prticular device.
Also read - > multipathing user-space tools like multipath , dmsetup , dmraid , udev , hotplug.