In a hybrid storage device comprising a fast tier and a slow tier, utilization of the fast tier is improved by dividing the fast tier into zones, including a zone for filesystem metadata, a zone for fast data, and a spillover zone for metadata, fast data or a combination thereof. By reducing the size of zones used exclusively for one type of data, while allowing both metadata and fast data to be stored in the spillover zone when necessary, better use of the fast tier is achieved. In another embodiment, a filesystem allocator is passed a policy object from which bands of storage are enumerated. The filesystem allocator iterates over the enumerated bands, searching for space to satisfy the allocation request.