Command balancing and interleaving for write and reads between front end and back end of solid state drive

In a data storage device having a non-volatile semiconductor storage device and a controller including a first interface and a second interface, a method of issuing read requests through the second interface to read data from the non-volatile semiconductor storage device in response to a sequence of read commands received from a host through the first interface, said method comprising:

• separating the read commands received from the host into a first read command having a read size larger than the read threshold size and a second read command having a read size smaller than the read threshold size, and storing the first read command in a first queue and the second read command in a second queue;
• issuing first and second read requests in succession through the second interface to read data of a predetermined size for reading less than the read threshold size, from the non-volatile semiconductor storage device;
• upon receiving a read response in response to the issued first read request, updating first tracking data for the first read command, the first tracking data including a first read size, which is equal to the read size of the first read command, and a first cumulative size, and removing the first read command from the first queue when the first cumulative size plus the predetermined size for reading equals the first read size;
• and
• upon receiving a read response in response to the issued second read request, updating second tracking data for the second read command, the second tracking data including a second read size, which is equal to the read size of the second read command, and a second cumulative size, and removing the second read command from the second queue when the second cumulative size plus the predetermined size for reading equals the second read size.

In a data storage device having a non-volatile semiconductor storage device and a controller including a first interface and a second interface, a method of issuing write requests through the second interface to write data into the non-volatile semiconductor storage device in response to a sequence of write commands received from a host through the first interface, said method comprising:

• separating the write commands received from the host into a first write command having a write size larger than the write threshold size and a second write command having a write size smaller than the write threshold size, and storing the first write command in a first queue and the second write command in a second queue;
• issuing first and second write requests in succession through the second interface to write data of a predetermined size for writing less than the write threshold size, into the non-volatile semiconductor storage device;
• upon receiving a write response in response to the issued first write request, updating first tracking data for the first write command, the first tracking data including a first write size, which is equal to the write size of the first write command, and a first cumulative size, and removing the first write command from the first queue when the first cumulative size plus the predetermined size for writing equals the first write size;
• and
• upon receiving a write response in response to the issued second write request, updating second tracking data for the second write command, the second tracking data including a second write size, which is equal to the write size of the second write command, and a second cumulative size, and removing the second write command from the second queue when the second cumulative size plus the predetermined size for writing equals the second write size.