Research On Hybrid File System For Solid State Storage Devices

Traditional disk-based storage systems fail to meet the performance requirement of the big data era due to the mechanical components.With the rapid development of storage technology,a series of new storage devices which have faster read and write speeds than disks appear,such as Flash-based Solid State Drive(SSD),Non-Volatile Memory(NVM).However,existing system softwares which are designed for disks fail to perform in SSDs and NVMs efficiently.Considering the different characteristics of SSD and NVM in terms of performance,capacity and price,a hybrid file system called NOCFS based on SSD and NVM is proposed.Since traditional black-box SSDs have the limitation that the hardware information is opaque to the upper layer software,NOCFS is designed for Open-Channel SSDs,which expose the hardware informantion to upper-layer software.NOCFS decouples file system metadata and data access path.The file system metadata is stored on NVM,and the ordinary data is stored on Open-Channel SSD.To fully exploit the performance advantages of NVM,NOCFS stores popular access data(hot data)on NVM.NOCFS uses Two-Queue algorithm combined with a statistic-based heat calculation method to identify hot data and cold data,and writes the cold data in NVM back to Open-Channel SSD.In order to efficiently write the co ld data in NVM back to Open-Channel SSD,NOCFS proposes a parallel-aware multi-thread data synchronization scheme.In addition,NOCFS designs a coordinated garbage collection mechanism to improve the efficiency of garbage collection,thus fully utilizing the white-boxing features of Open-Channel SSD device.The experimental results show that,with a small amount of NVM,NOCFS greatly improves the I/O throughputs under different workloads,compared with the existing SSD-based file system F2 FS.When the amount of NVM grows,NOCFS's performance improves until it matches the performance of NVM-based file system PMFS.