All three types of multipathing software provide comparable levels of reliability.
Where they primarily differ is in terms of performance via load-balancing
Storage vendors, of course, claim that their solutions are better because
they are more tightly integrated with the subsystem hardware, but the
differences in efficiency and reliability are generally minimal.
Storage vendors claim that they take advantage of API calls to query the
storage subsystem to obtain traffic statistics. This allows the multipathing
software to more accurately determine how to balance the traffic, and
may also help ensure seamless recovery from a path failure.
However, VERITAS DMP also understands APIs for several subsystem
vendors and can use this ability to load-balance more effectively. Of course,
for JBODs and unsupported subsystems, DMP uses a simpler method.