A storage device includes a first memory having a first access speed, a second memory having a second access speed slower than the first access speed, and a processor coupled to the first memory and the second memory and configured to copy one or a plurality of first data blocks included in a plurality of data blocks stored in the first memory, to the second memory, determine whether a processing amount per unit of time in the first memory reaches a threshold value based on a limit value of the processing amount when the processor receives a read request of a second data block included in the first data blocks, and read the second data block from the first memory when the processing amount does not reach the threshold value, and read the second data block from the second memory when the processing amount reaches the threshold value.