Under the present invention, a small cache is used for the selective buffering of devices of a heterogeneous striping group (i.e., striping group made of devices with unequal capacities) to match the load on each device to its capacity. The inventive caching algorithm utilizes a device map, or disk map, and applies a cache distribution factor for each device of a group to determined how to selectively buffer blocks read from different devices of a striping group; thereby placing different loads on the different devices of a striping group in accordance with their capacities.