The Design And Implementation Of Wear Leveling For Inode In NVM-based In-memory File System

In recent years,a new type of non-volatile memory(NVM),such as phase change memory,resistive memory,etc.,has byte addressable,low power consumption,and high storage density.The features make NVM a huge potential for storage-level memory.Existing persistent memory file systems such as PMFS?SIMFS and NOVA,achieve high-performance file accesses by exploiting high speed and byte addressability of emerging persistent memories,However,NVM has a limited useful life.If you continue to perform a write operation on a fixed area of NVM,NVM will be quickly written and the data in the area will be lost,which will seriously affect the stability of the entire storage system.However,these persistent memory file systems ignore the limited write endurance of PMs.File operations are local and frequent and can easily damage NVM storage units.Particularly,the frequently updated inodes are stored on fixed physical locations throughout their lifetime,which can easily damage PM device with common file operations.To address such issues,we propose a new mechanism,Virtualized Inode(VInode),for the wear leveling of inodes of persistent memory file systems.The main idea of VInode is to unbind the logically and physically of the inodes and dynamically change the mapping relationship between the logical space of the inode and the physical space,so that a large number of update operations of the logical inode can be evenly distributed to the physical space.To avoid excessive wear on a single physical location.VInode consists of two key techniques.First,Inode-virtualization enables a logical inode to be remapped to any physical inode during runtime.Second,Inode-migration evenly distributes writes of inodes to PM by dynamically migrating the heavily written inodes to the less written pages in PM.In Inode-migration,we develop an algorithm called Pages as Communicating Vessels(PCV)to efficiently find and migrate the heavily written inodes.We implement VInode in SIMFS(VInode-PCV),a typical persistent memory file system and using the typical file system testing tools Filebench and FIO.Experiments are conducted with well-known benchmarks.Compared with original SIMFS,experimental results show that VInode-PCV can reduce the maximum value and Coefficient of Variation of the write counts of pages to 1000 x and 537 x lower,respectively.At the same time,only additional write operations with a maximum of 3.96% and performance overheads of no more than 4.5% are carried.The experimental results show that the VInode technology achieves a good wear leveling effect.