Design And Implementation Of A File System Called Trinityfs For A Hybrid Storage Device

With the development of Internet and the technology of computer storage, people havethe increasingly high demand for information storage systems, such as High-speed I/Operformance, low power consumption, strong fault-tolerance and the ability to recover data.At present, the existing disk-based storage systems can not meet the above requirements,therefore we repose our hopes on the emerging new type of storage media, such as flash,phase change memory. The emergence of a new medium enhances the performance on someattributes of the storage system, but because each of the media’s characteristics or limitationsof the manufacturing process, the introduction of new media will bring the system some ofthe other constraints.Considering the characteristics of traditional disk, flash memory and phase changememory on performance, capacity, reliability, energy consumption and cost, we designed afile system called TrinityFS for a PCRAM-Flash-HDD hybrid medium. Firstly the PCRAMhas the I/O performance close to memory, byte-level read and write granularity. But due tothe limitations of current technology and production process, this medium has tiny capacityand is expensive. So we put the metadata which is most frequently read, written and updatedbut accounted for a very small capacity on the PCRAM, then accessing metadata can reachthe speed of RAM level. Secondly, due to the large capacity of the hard disk which has agood sequential write performance, and compared to the flash memory the hard disk has alonger life, we try to redirect write operations to the disk in a log way to reduce the updateand erase operations on flash. Thirdly, flash memory has the advantages of high-performance,low power consumption, high reliability and seismic, and compared to the the hard disk,flash memory has a better read performance, so we regularly scan the data on disk to find thehot read data and then migrate them to the flash in order to improve the overall performance.Based on file system LogFS, we implemented TrinityFS, then we did some test work onit. The results show that TrinityFS enhances the overall performance of the storage systemunder different workloads.