The explosive growth of information worldwide emerges as a great challenge for the currently-available big data center platform and compels the development of novel methods and storage devices. Far-field super-resolution techniques have shown the potential to achieve nanoscale three-dimensional optical data storage resulting in a single-disc capacity towards petabytes. In particular, super-resolution photoinduction-inhibited nanolithography (SPIN) has been used to write features with size of 9 nm, while stimulated emission depletion (STED) microscopy is suitable for super-resolution optical data reading. However, the combination of SPIN and STED microscopy for super-resolution optical data storage is presently limited by the high intensity required for the inhibition beam, which results in high energy consumption and damage of the data bits, and the lack of an optically-activatable material for data read-out after SPIN. Recently, rare-earth doped nanocrystals, featuring long luminescence lifetime and emission bands ranging from ultraviolet to near-infrared, have been proven adapt for low-power super-resolution optical data reading through STED microscopy and may be implemented for super-resolution data writing fully based on optical methods. Here, we report about the development of rare-earth doped nanocrystals for ultra-low power, ultra-high capacity super-resolution optical data storage. Core-shell nanoparticles were prepared via co-precipitation and measurements of emission intensity and fluorescence lifetime have been performed. Subsequently, rare-earth doped nanocrystals have been used for optical data storage under 980-nm laser excitation and the data bits were successfully retrieved back by STED microscopy. Finally, simulation results indicate the feasibility of nano-sized recordings and thus a boost of storage capacity is expected.