A storage device including: a nonvolatile memory device including a plurality of nonvolatile memory cells, a partial storage area and an overprovision storage area; and a controller configured to control the nonvolatile memory device, wherein when the controller detects a fault of the nonvolatile memory device, the controller negates the partial storage area, reassigns the overprovision storage area, which corresponds to a size of a user area, among the partial storage area, determines a device fail if the overprovision storage area is less than an overprovision threshold after the reassigning of the partial storage area, and determines a recovery success if the overprovision storage area is equal to or greater than the overprovision threshold after the reassigning of the partial storage area.