Memory system, control method thereof, and program

A memory system connectable to a host, comprising:

• a nonvolatile memory configured to execute one of a plurality of read operations including a first read operation and a second read operation, the first read operation taking a first time period to complete reading data from a physical address, the second read operation taking a second time period longer than the first time period to complete reading the data from the physical address, a reliability level of data read by the first read operation being lower than a reliability level of data read by the second read operation;
• and
• a memory controller configured to issue a read command to the nonvolatile memory to cause the nonvolatile memory to execute one of the plurality of read operations,
• wherein the memory controller is configured to:
• select, on the basis of a reliability level of data to be read from a first physical address, one of the first and second read operations to be executed by the nonvolatile memory first in a read sequence corresponding to a read request received from the host, and
• instruct the nonvolatile memory to execute the selected read operation from the first physical address.