The airborne frequency-modulated continuous-wave synthetic aperture radar presents an enormous technical challenge on the design of data storage system due to its characteristics of high-data rate, small size, light weight, and low-power consumption. There are two main problems for the high-speed storage under the miniature requirement. One is the unpredictable response time of the flash translation layer in the CompactFlash card. The other is the relatively long response time of the file system. This paper designs a data storage system in a real-time signal processor. Two techniques called configurable buffer structure and FPFQA (FAT pre- and FDT quasiallocation) are presented to overcome these two problems. The evaluated performance indicates that the size, power consumption, and weight meet the miniature requirement, while the function of the high-speed data storage with approximately storage speed and real-time file management are realized.