HighLight: Using a Log-structured File System for Tertiary Storage Management

Log-structured file systems (LFSs) were developed to eliminate latencies involved in accessing disk devices, but their sequential write patterns also match well with tertiary storage characteristics. Unfortunately, existing versions only manage memory caches and disks, and do not support a broader storage hierarchy. Robotic storage devices offer huge storage capacity at a low cost per byte, but with large access times. Integrating these devices into the storage hierarchy presents a challenge to file system designers. HighLight extends 4.4BSD LFS to incorporate both secondary storage devices (disks) and tertiary storage devices (such as robotic tape jukeboxes), providing a hierarchy within the file system that does not require any application support. This report presents the design of HighLight, proposes various policies for automatic migration of file data between the hierarchy levels, and presents initial migration mechanism performance figures. Log-structured file systems, with thei..