Recording density, domain switching time and bit error rate were evaluated using a data storage system based on scanning nonlinear dielectric microscopy. Congruent lithium tantalate single crystals with the thickness less than 50 nm were used as recording media. Local domain switching was carried out by applying voltage pulse on the recording media using a conductive cantilever. Close-packed domain dot arrays were written on the recording media. As a result of optimizing the writing pulse conditions, the dot array with the areal recording density of 10.1 Tbit/inch2 was successfully written. Subsequently, the thickness of recording media was reduced in order to improve the domain switching property, which determines the upper limit of data transfer rate. A nanodomain dot was formed by applying a 500-ps pulse on the 18-nm-thick recording medium. Actual information data were recorded for bit error tests. There were no bit errors in approximately ten-thousand-bit data under the areal recording density of 258 Gbit/inch2. It means bit error rate was less than 1×10-4. Additionally it was also confirmed that actual information data was recorded at the areal recording density of 0.98 Tbit/inch with a few bit errors.