According to one embodiment, a device includes a determination unit, compression unit, selecting unit, write updating unit, writing unit. The determination unit determines whether to compress write data based on specific information. The specific information including at least one of the type, number of accesses, access frequency and importance level of the write data. The compression unit compresses the write data when determining to compress the write data. The selecting unit selects a write region for the write data in nonvolatile memory based on the specific information. The write updating unit updates the specific information. The writing unit writes compressed write data into the write region when determining to compress the write data. The writing unit writes uncompressed write data into the write region when not determining to compress the write data.