Key Technologies Of NVM Block Driver For Traditional File Systems

New non-volatile memory(NVM)is promising to be the next generation of storage media.NVM has DRAM-like access speed and is byte-addressable like DRAM.NVM can serve as both main memory and external storage.It's full of challenges and opportunities to integrate NVM into the existing computer architecture.A NVM block driver uses NVM to simulate a block device,which can be utilized by traditional file systems.The NVM block device can improve file system performance for a thousand times compared to traditional block devices.However,there are some problems when traditional file systems use NVM.Due to user habits and high frequency access of file system metadata,there is a serious imbalance of block write in traditional file systems.And,when file systems write data,sudden power failure may cause partial data modification of a data block.Lastly,it's common for user applications to access data by file cache IO.There is a data copy between page cache and NVM in file cache IO,which is unnecessary and reduces file system performance.In this paper,we implement a NVM block driver(NVMBD).To solve the problems above,we develop a translation layer optimization technology and a block IO request processing optimization technology in NVMBD.The translation layer optimization technology uses a translation layer to achieve NVM wear-leveling and the atomicity of block write.The translation layer achieves the mapping between logical blocks and physical blocks in NVM.The translation layer distributes repeated writes on a logical block to many physical blocks,which achieves the wearleveling of NVM.Translation layer updates data by cow(copy-on-write)technology and uses journaling to ensure the atomicity of mapping establishment,which achieves the atomicity of block writes.The block IO request processing optimization technology can rapidly process some specific block IO requests.It maps NVM space to page cache instead of copying data between NVM space and page cache.In our experiments,it can double file system performance.