Research And Design Of PCRAM-based Hybrid Storage System

In today’s storage system, the mainline memory is still the traditional disk and SolidState Disk (SSD) based on Flash. However, the reading and writing performance of thetraditional disk is poor because of the limitation of the internal mechanical structure.Although SSD has made a lot of improvements, writing data is the biggest drawbacks inits performance for that it must do block erase before writing data. Phase change memory(PCRAM) is a new type of non-volatile memory semiconductors which takes use of thedifferent resistivity of phase change alloy material in the state of crystal and amorphous tostore binary data. PCRAM has many advantages such as higher storage density, fasterspeed in reading and writing, no block erase operation and longer life, which meets theneeds of the future high performance storage.This paper designs a kind of high performance memory through composite theadvantages of SDRAM, FLASH and PCRAM, which consists of the hybrid memorysystem and the hybrid storage system.The hybrid memory system consists of SDRAM andPCRAM has advantages of both the high speed of SDRAM and the non-volatilecharacteristic of PCRAM, meanwhile, the hybrid storage system consists of PCRAM andFLASH has advantages of both the high speed of PCRAM and the high-capacity andlow-cost of FLASH. Because of using the interface technology of DDR3and PCIE, thishybrid storage system achieves high speed of data transmission.According to the characteristics of the PCRAM, this paper designs the systemhardware architecture and the hierarchical structure of the hybrid storage and the arraystructure of the PCRAM. The logic structure of hybrid memory system is detailedexpound and and the hardware circuit of hybrid storage system is designed andimplemented. A high effective hybrid storage controller based on CPLD is also designed.In the work mode of PEX8311interface chip, we achieve the single cycle access andDMA data transmission for the storage array. This paper realizes the device drivers of thehybrid storage system in the Linux operation system. Finally, compared with thetraditional disk and SSD, the performance test of this hybrid external storage is done.