Methods for generating a characterizing summary and generating a collection of relevant preservation objects in a preservation system are provided. The disk drive further comprises a head comprising a plurality of read sensors including a first read sensor, and a second read sensor separated from the first read sensor by a down-track spacing. , an aliphatic quaternary ammonium salt of the formula, an organic solvent and a lithium salt of the formula, the electrolytic solution being characterized in that the organic solvent contains vinylene carbonate in an amount of 1 to 5 wt. A switch may be used to energize the LED.