Embodiments of the present invention provide methods, computer systems, and computer program products for adjusting allocation of a storage device. In one embodiment, a first part of the storage device is allocated to tiering storage, and a second part of the storage device is allocated to cache storage. Operating statuses of the first part and second part are collected. A performance measure of the first part is obtained based on the operating status of the first part, and a performance measure of the second part is obtained based on the operating status of the second part. Allocation of a capacity of the storage devices is adjusted between the first part and the second part based on the performance measures of the first part and the second part.