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