Research On Intelligent Coupling Of Dual-mode Flash Memory And Hard Disk Drive For Hybrid Storage

The ascension speed of disk access cannot meet the demand of access requirements of huge amounts of data in big data era, which gradually becomes the key factors that affecting the performance of computer system. The appearance of flash memory provides a new direction of development for the storage system, but the cost of flash memory is too high to promote in a large scale. Based on this, it has become one of the hot research topic in combination with individual advantage of flash memory and HDD. At present, flash memory includes Single-Level Cell(SLC) and Multi-Level Cell(MLC). The SLC has characteristics of high cost, small volume, and high speed. The MLC has characteristics of low cost, large capacity, and slow speed.This paper proposed a dual-mode flash memory hybrid storage system(DMFMHS). It is based on the content locality principle, the data is divided into two types: the reference data which is focus on read operation and the delta data which is focus on write operation. The former will be stored in SLC; the warm or cold data(delta data) is stored in MLC or disk sequentially according to the degree of data hotness or coldness(The system intelligently identifies hot and cold data and does data migration between MLC and disk); the metadata organizes the mapping physical location of reference block and the delta data of the original data block.We have implemented the DMFMHS based on the device mapper plugin with other mixing storage solution. The test results show that the new hybrid storage scheme effectively improves the data access speed and reduces the response time compared with Flashcache storage structure. Simultaneously DMFMHS also has 10% improvement of the performance in relative to the storage solution that does not cache the thermal delta data.