CREATE TABLE table_name_67 (controller VARCHAR(255), nand_type VARCHAR(255), seq_read_write_mb_s VARCHAR(255))
Which controller is NAND type 25nm mlc-het with sequential read/write MB/s of 270/210?
    
SQL: SELECT controller FROM table_name_67 WHERE nand_type = "25nm mlc-het" AND seq_read_write_mb_s = "270/210"