HashTag: Fast Lookup in a Persistent Memory File System

Abstract

Persistent Memory (PM) offers byte-addressability and persistence on the memory bus, and delivers dramatic performance improvements over traditional storage media. While many file systems have been optimized for PM, a large fraction of processing time is generally spent locating the required data in PM due to the standard use of extent-trees for location indexing. This paper presents HashTag, a cache of PM locations for use in PM file systems with support for snapshot creation. We evaluate HashTag across a range of configurations to determine the impact of various location caching options on filesystem performance. These lessons can inform the design of future caching solutions in PM filesystems.