Method, apparatus, and computer program product embodiment for allocating a plurality of extents in a thinly provisioned computing storage environment are provided. In one such embodiment, subsequent to a write request and previous to entering a cache of the computing storage environment, a determination is made, for a logical extent, whether a real extent is available. Pursuant to determining the availability of the real extent, the logical extent is allocated to the real extent by updating system metadata associated with the logical extent.