Performance-degrading hardware components in computer storage systems are identified. A timed-out input/output (I/O) operation is detected. Hardware components that include a plurality of types of hardware components involved with the timed-out I/O operation are identified. Involve counts of the hardware components are increased. A plurality of suspicious hardware components are identified based, at least in part, on a hardware hierarchy including one or more types of hardware components. There is at most one suspicious hardware component for each type of hardware component. A performance-degrading hardware component is identified from among the plurality of suspicious hardware components based, at least in part, on the involve counts and the hardware hierarchy. The performance-degrading hardware component is in a layer of the hardware hierarchy that is lower than layers including other suspicious hardware components.