A method of operating a memory controller includes; counting a number of read operations directed to a page-group of data stored in a block and generating a first read count number, then comparing the first read count number with a first reference count threshold among a first set of reference count thresholds associated with the page-group, and upon determining that the first read count number exceeds the first reference count threshold, performing a copy-back operation of the page-group data from the block to another block.