selecting {HEAD ~ at least some} of {TAIL ~ the storage arrays}, a combined available performance capability of which is at least equal to the performance requirements for the logical data volume 
of
selecting { HEAD ~ at least some } of { TAIL ~ the storage arrays } , a combined available performance capability of which is at least equal to the performance requirements for the logical data volume
OTH HEAD HEAD 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 OTH OTH OTH OTH