Embodiments of the present invention provide a method, system, and computer program product for allocating storage extents. Extent input/output information pertaining to an extent on a storage device is received, by a computer, where the extant input/output information includes an access rate of data stored on the extent. The computer determines one or more periods of time where the input/output information exceeds a preconfigured threshold. The computer generates one or more of a first policy and a second policy based on the determined one or more periods where the first policy includes allocating the extent to a high performance disk within a tier storage system when data is stored during the determined periods and the second policy includes reallocating the extent from a low performance disk within the tier storage system to a high performance storage device within the tier storage system during the one or more determined periods.