This object is the 64-bit counterpart to storageIONRead, tracking cumulative bytes read from this device since boot without the 32-bit counter's wraparound limit. Admins on high-throughput NAS units prefer polling this counter for accurate long-term read totals, since a busy 32-bit counter can wrap multiple times between polls. For example, on a device sustaining multi-terabyte transfers, storageIONReadX keeps counting accurately where storageIONRead would roll over.