Title: Analyzing IO Amplification in Linux File Systems,
Abstract: We present the first systematic analysis of read, write, and space
amplification in Linux file systems. While many researchers are tackling write
amplification in key-value stores, IO amplification in file systems has been
largely unexplored. We analyze data and metadata operations on five widely-used
Linux file systems: ext2, ext4, XFS, btrfs, and F2FS. We find that data
operations result in significant write amplification (2-32X) and that metadata
operations have a large IO cost. For example, a single rename requires 648 KB
write IO in btrfs. We also find that small random reads result in read
amplification of 2-13X. Based on these observations, we present the CReWS
conjecture about the relationship between IO amplification, consistency, and
storage space utilization. We hope this paper spurs people to design future
file systems with less IO amplification, especially for non-volatile memory
technologies.