A system and method for allocating data objects across multiple physical storage devices in a mass storage subsystem first determines a set of physical properties associated with the physical storage devices. The system assigns portions of the mass storage subsystem to a first division or a second division based on the physical properties, such that read operations directed to logically related data stored in the first division can be executed more efficiently than read operations directed to data stored in the second division. During operation, the system stores data objects with a low SLR in the second division, which may be allocated according to any well-known file system. If a write request is for a new data object with a high SLR, the system stores the new data object in a set of neighboring primary data chunks in the first division. For subsequent write requests that modify a stored data object, the system stores the modified data in a spillover data chunk located in proximity to the primary data chunk.