Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_6314 ( "Model" text, "Codename" text, "Capacities (GB)" text, "NAND type" text, "Interface" text, "Form factor" text, "Controller" text, "Seq. read/write MB/s" text, "Rnd 4KB read/write IOPS (K)" text, "Introduced" text )

### Question ###
Which controller is NAND type 25nm mlc-het with sequential read/write MB/s of 270/210?

### Accurate SQL ###

SELECT "Controller" FROM table_6314 WHERE "NAND type" = '25nm mlc-het' AND "Seq. read/write MB/s" = '270/210'