by external power supplied e g by the host 110 which powers the entire ssd 130 in one embodiment the host 110 is configured to control the power to the ssd 130 and may shut off power to the ssd 130 during certain time intervals to reduce the power consumption of the system referring to fig4 the edlc 210 may include a real time clock 410 a watchdog timer 420 one or more sensors 430 an edlc controller 440 and non volatile memory nvm 450 in operation the edlc controller 440 may periodically read the sensors 430 and the real time clock 410 and collect e g record time tagged sensor readings such as temperature readings in the nvm 450 in other embodiments the host 110 may contain an environmental data logging system data logged by which may be used instead of or in addition to data logged by the edlc 210 to determine when data items are nearing expiration in one embodiment the edlc 210 may be integrated into the ssd controller 140 provided that it is implemented in a dedicated power island so that power may be provided to the edlc 210 without providing power to the entire ssd 130 which would result in excessive power consumption referring to fig5 in one embodiment in which the edlc 210 has and is able to operate on power supplied from a battery 240 avoiding expiration of data items is accomplished using the method illustrated in which the host powers up the ssd 130 as needed to prevent expiration of data in an act 510 the host operates a host timer until a set interval referred to as a shutdown interval has expired during this time.