  Data compression has been widely adopted to release mobile devices from
intensive write pressure. Delta compression is particularly promising for its
high compression efficacy over conventional compression methods. However, this
method suffers from non-trivial system overheads incurred by delta maintenance
and read penalty, which prevents its applicability on mobile devices. To this
end, this paper proposes DeltaFS, a metadata-enabled Delta compression on
log-structured File System for mobile devices, to achieve utmost compressing
efficiency and zero hardware costs. DeltaFS smartly exploits the out-of-place
updating ability of Log-structured File System (LFS) to alleviate the problems
of write amplification, which is the key bottleneck for delta compression
implementation. Specifically, DeltaFS utilizes the inline area in file inodes
for delta maintenance with zero hardware cost, and integrates an inline area
manage strategy to improve the utilization of constrained inline area.
Moreover, a complimentary delta maintenance strategy is incorporated, which
selectively maintains delta chunks in the main data area to break through the
limitation of constrained inline area. Experimental results show that DeltaFS
substantially reduces write traffics by up to 64.8\%, and improves the I/O
performance by up to 37.3\%.
