A Consistency Mechanism For NVM-based In-Memory File Systems

With the development of material technology,Non-Volatile Memory(NVM)has evolved to provide power consumption and latency comparable to Dynamic Random Access Memory(DRAM).This breakthrough makes both industry and academia begin to reflect NVM's implication on a new generation of system software,including NVM-based in-memory file systems.Based on such kind of file systems,this paper studies the design of consistency mechanism,which includes the design of underlying storage model,critical system operations to cover and corresponding optimizations.For NVM-based in-memory file systems,data on durable storage device can be directly accessed by CPU.This kind of direct access,on the one hand,eliminates doubled copy from memory to storage device in traditional file systems,which considerable improved the overall throughput.But on the other hand,it cannot be adapted to the consistency mechanism of traditional file systems.New challenges arises with such inconsistency problems.This paper based on such problem,proposed a brand new consistency mechanism that can be applied to NVM-based in-memory file systems.This mechanism is based on a layered abstraction of NVM storage device,using lazy-validated snapshot strategy to guarantee the integrity of data.Also,it covers critical system operations like file read/write and snapshot taking/removal,provides recovery methods for arbitrary crashes.At the same time,this paper provides optimization methods for proposed mechanism.Those optimizations effectively reduced the extra cost of consistency guarantees.Comparing to some existed designs,our mechanism can reduce the storage cost and latency of critical system operations.Also,it performs better in multi-threaded scenarios and is more friendly to DRAM.