According to an aspect, a method for key-value storage includes determining whether a data size of a first set comprising data and a key stored in a first area or a second area of a first storage unit is larger than a threshold determined for the first area or the second area in which the first set is stored, as a first execution condition. The method further includes determining whether a degree of collisions of a hash value indicating a storage location of the first set in the first area of the first storage unit is greater than a predetermined threshold, as a second execution condition. When the set satisfies either of the first or second execution conditions, the method includes the first set in the second area.