In SU-MIMO, even when the channel state of one antenna is poor, an error ratio is improved by obtaining a transmission antenna diversity effect. A cache control is configured to respond to a requested capacity upgrade, establishing a capacity restriction applicable to a filesystem providing active perceived available capacity spanning the disk drive subunits, such as drawers, blades or disk drives. The pack is adapted to deploy a single flare at a time. The rings define a shielding coaxial structure for the via-hole. The AC and DC components of the optical signal are detected.