Removing fsync from our local storage engine
Summary
FractalBits discusses removing fsync from a local storage engine to achieve crash-consistent writes without fsync by using fixed-size pre-allocated files, O_DIRECT writes, and an SSD-aware journal. The architecture comprises an in-memory index, a journaling layer, and a data area, with 4KB atomic journal commits under a device contract. Reported 4KB random-write throughput improvements over ext4 with fsync indicate significant tail-latency benefits, though the approach requires narrowing the SSD durability contract and is not suitable for HDDs or general-purpose KV workloads.