Abstract: Most file systems overwrite modified file data and
metadata in their original locations, while the Log-structured File
System (LFS) dynamically relocates them to other locations. We
design and implement the Evergreen file system that can select
between overwriting or relocation for each block of a file or metadata.
Therefore, the Evergreen file system can achieve superior write
performance by sequentializing write requests (similar to LFS-style
relocation) when space utilization is low and overwriting when
utilization is high. Another challenging issue is identifying
performance benefits of LFS-style relocation over overwriting on a
newly introduced SSD (Solid State Drive) which has only
Flash-memory chips and control circuits without mechanical parts.
Our experimental results measured on a SSD show that relocation
outperforms overwriting when space utilization is below 80% and vice
versa.