The documentation for the "SUN StorEdge Fast Write Cache" (FWCache)
product states that one should "avoid multiple paths to the data".
 
This wording has been the cause of concern among Veritas Volume Manager
users who use Volume Manager's DMP capability.                         

However, there is no need for concern.  Using DMP and FWCache together
is fine.
 
What is meant by "multiple paths" is one path THROUGH the cache and
another path AROUND the cache.
 
For example, if you have a disk referred to as c1t0d0 and a second path
as c2t0d0, and you cache all reads and writes to c1t0d0 but do not
cache reads/writes from/to c2t0d0, data corruption could occur.
 
Everything is fine as long as it is the Volume Manager volumes that are
being cached.  Since VxVM and DMP are all below (logically speaking)
the FWCache, everything is fine.      

Keywords: VxVM, Volume Manager, DMP