Memory system

A method, comprising:

• selecting logical blocks of garbage collection target candidates based on respective numbers of valid data in a plurality of logical blocks of a memory;
• calculating a maximum value among the numbers of valid data for a plurality of banks in each of the logical blocks of the garbage collection target candidates as a respective comparison value;
• selecting one of the logical blocks of the garbage collection targets based on comparing the respective comparison values of the logical blocks of the garbage collection target candidates with each other;
• adding the number of valid data for each bank in each of the logical blocks to the number of valid data for each bank of one of the logical blocks of the garbage collection targets;
• and
• determining a maximum value among the added numbers of valid data for the banks of each of the logical blocks as the comparison value;
• wherein as the result of comparing the respective comparison values of the logical blocks of the garbage collection target candidates with each other, when there are a plurality of logical blocks of the garbage collection target candidates having a minimum comparison value, the controller selects, as the logical block of the garbage collection target, the logical block of one garbage collection target candidate among the logical blocks of the garbage collection target candidates having the minimum comparison value, and selects the logical blocks of other garbage collection target candidates as the logical block of the garbage collection target from the next time.

A memory controller configured to:

• select logical blocks of garbage collection target candidates based on respective numbers of valid data in a plurality of logical blocks, wherein a memory, coupled to the memory controller, stores the number of valid data in each of the logical blocks and a number of valid data for each of a plurality of banks in each of the logical blocks;
• calculate a maximum value among the numbers of valid data for the banks in each of the logical blocks of the garbage collection target candidates as a respective comparison value;
• select one of the logical blocks of the garbage collection targets based on comparing the respective comparison values of the logical blocks of the garbage collection target candidates with each other;
• add the number of valid data for each bank in each of the logical blocks to the number of valid data for each bank of one of the logical blocks of the garbage collection targets;
• and
• determine a maximum value among the added numbers of valid data for the banks of each of the logical blocks as the comparison value;
• wherein as the result of comparing the respective comparison values of the logical blocks of the garbage collection target candidates with each other, when there are a plurality of logical blocks of the garbage collection target candidates having a minimum comparison value, the controller selects, as the logical block of the garbage collection target, the logical block of one garbage collection target candidate among the logical blocks of the garbage collection target candidates having the minimum comparison value, and selects the logical blocks of other garbage collection target candidates as the logical block of the garbage collection target from the next time.