1. A storage device comprising: a nonvolatile memory device comprising a plurality of memory blocks, each of which comprises string selection transistors connected to a plurality of string selection lines, ground selection transistors connected to a plurality of ground selection lines, and memory cells connected to a plurality of word lines; and a controller configured to read valid data groups of a first memory block, among the memory blocks, and write the valid data groups in a second memory block, among the memory blocks, during a read reclaim operation, wherein the controller assigns first locations of the second memory block, at which the valid data groups are written, based on read counts of the valid data groups.