The invention provides methods and compositions for measuring the formation of scale within a process system. The subsystem furthermore has a circuit that is responsive to a predicted failure indication by a data storage device in relation to predetermined rules stored in memory for deterministically initiating a preventive recovery either by a data recovery procedure in the data storage device or by a fault tolerance storage arrangement in the subsystem. Under the grid is a movable array of light sensors and temperature sensors. A context for a message is defined that allows DMA controllers of the CPD to move data, free of headers, directly to or from a destination or source in the host. The other of the push and pull operations is performed with an output current of the current mirror circuit. The darkening curve may be implemented as a formula or a look-up table in software or drive electronics that energize the transmissive LCD.