An SMR-Aware Append-Only File System

The advent of shingled magnetic recording (SMR) is bringing significant changes to modern file system design. Update-in-place data structures are no longer practicable; log structuring is becoming the de facto game. We report on simulations of a new SMR aware file system for append-only or circular write-only environments that merges log-structured design with traditional journaling to the advantage of both techniques. For example, sequential read performance should be better with SAFS than with a pure LFS because with SAFS, compaction moves blocks of data to contiguous zones. And, like a pure LFS, write performance should be high because writes are converted to appends to a single zone at a time. In this talk, we discuss the effects that SMR is having on basic file system design, how we arrived at our hybrid design, simulations of the design, and results we’ve obtained to date, especially a comparison of the performance of a simulation of SAFS, a traditional journaling file system, and an LFS, all under Linux.

Learning Objectives

SMR Disk Technology Overview and its Effect on File Systems
SMR Disk Technology and Log-structuring File Systems
SMR Disk Technology and Append-only File Systems