This counter indicates the number of times this physical drive performed an action that violated the SCSI-2 bus protocol, an event that forces the SCSI bus to reset, with 4,294,967,295 returned if the value cannot be determined. An admin watches this because a bus reset caused by one misbehaving drive can briefly disrupt I/O to every other drive sharing that bus. For example, a rising bad-target count on one disk that correlates with intermittent slowdowns across the whole array points to that drive as the culprit forcing bus resets.