1. A method, comprising: maintaining, by a storage controller, an allocation space for extent space efficient storage volumes, in response to a request from a host application for storage space, wherein an extent pool is configured to allocate available extents to the host application; in response to a request from the host application to delete data stored in selected extents that are already allocated to the host application, deleting the data but continuing to maintain the selected extents as being allocated to the host application; in response to a request to write new data, writing the new data to the selected extents that are already allocated; determining that a predetermined period of time has elapsed since the data was deleted; and releasing the selected extents to add to the extent pool, in response to determining that the predetermined period of time has elapsed since the data was deleted.