Table schema:
CREATE TABLE table_name_67 (controller VARCHAR, nand_type VARCHAR, seq_read_write_mb_s VARCHAR)

Question: 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"