wherein {HEAD ~ any} of {TAIL ~ the storage arrays} may take over as the primary device in response to sensing a failure of the primary device 
of
wherein { HEAD ~ any } of { TAIL ~ the storage arrays } may take over as the primary device in response to sensing a failure of the primary device
OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH