Since the Linux 4.14 kernel Btrfs has supported Zstd for transparent file-system compression while a revived patch-set would allow that Zstd compression level to become configurable by the end-user.

Facebook, which is behind Zstandard and also the employer for several key Btrfs developers, started off on the Zstd compression level support for Btrfs previously. This would allow users to use a higher compression level to achieve greater compression but at the cost of increased memory usage and obviously more resource intensive or opt for lower compression.

At the lowest Zstd compression level, the Btrfs integration could yield a compression ratio of 2.658 and a compression speed of 438MB/s or decompression at 910MB/s while at the highest level (15) the ratio was 3.126x while having a compression speed of just 37MB/s and decompression at 878MB/s.

The newest patches for offering a configurable Zstd compression level for Btrfs can be found on the kernel mailing list.