The compression options in Btrfs are great, and help save a ton of space on disk. Zstandard works extremely well for this, and is fairly fast. However, it can heavily reduce the speed of quick disks, does not work well on lower-end systems, and does not scale well across multiple cores. Zlib is even slower and worse on compression ratio, and LZO suffers on both the compression ratio and speed. I've been laying out my plans for a backup software recently, and stumbled upon LZ4. Tends to hover around LZO compression ratios. Performs better than Zstandard and LZO slightly for compression - but significantly outpaces them on decompression, which matters significantly more for users: zstd 1.4.5: - ratio 2.884 - compression 500 MiB/s - decompression 1.66 GiB/s zlib 1.2.11: - ratio 2.743 - compression 90 MiB/s - decompression 400 MiB/s lzo 2.10: - ratio 2.106 - compression 690 MiB/s - decompression 820 MiB/s lz4 1.9.2: - ratio 2.101 - compression 740 MiB/s - decompression 4.5 GiB/s LZ4's speeds are high enough to allow many applications which previously declined to use any compression due to speed to increase their possible space while keeping fast write and especially read access. What're thoughts like on adding something like LZ4 as a compression option in btrfs? Is it feasible given the current implementation of compression in btrfs? -Amy IP
