Storage class memory having low power, low latency, and high capacity

Direct attached dual in line memory (DIMM) card 102 contains dynamic random access memory (DRAM) 104, at least one of non-volatile memory 105-108 and a processor 110 selectively allocating data among the DRAM and the non-volatile memories based on the data set size. Such hybrid arrangement has low power and high capacity because of the non-volatile memories, such as solid-state memories, while low latency is obtained by distributing data-sets according to their size. Smaller data sets are placed in DRAM, medium sized data in phase change memory (PCM) 105, and large data-sets in NAND flash 108. Data-sets can also be straddled by partitioning them across different memory technologies. Data writes can involve buffering to DRAM, sending the data to the NAND flash 108, and then a selective migration among the memories. Other non volatile memories can include resistive RAM (ReRAM) 106 and spin transfer torque RAM (STT-RAM) 107.