Abstract: A system, method, and apparatus are provided for performing a transparent hybrid data storage scheme in which data are stored as blocks distributed among one or more flash-based storage devices (e.g., solid state drives) and one or more magnetic storage devices (e.g., magnetic disk drives). Files larger than a given size (e.g., 1 MB) are segmented into blocks of that size and stored on one or more devices; blocks of one file may be stored on devices of different types. Periodically, a utility function calculates utility values for each of some or all stored blocks based on frequency of access to the block, frequency of access of a particular type (e.g., random, sequential), a preference regarding where to store the block or the corresponding file, and/or other factors. Blocks having the highest utility values are subject to migration between devices of different types and/or the same type (e.g., for load-balancing).