If you are wanting a storage "as long as the power is there" then the 24 Bytes should normally fit on the on board RAM of the 8051.This will of course reduce your available variable storage space...

But in case you want to save the data between sessions then we are talking about a non volatile RAM like EEPROM or atleast have a battery back up for the MCU and enter low power mode when idle. The options are wide and large.

Raghu