Most network file systems are either a layer over an existing filesystem (NFS, CIFS), or are develped from scratch to have separate, replicated, purpose-designed databases for metadata and object store (GFS, Glusterfs). At the same time, most database engines provide (or can be coerced into providing) replication and all the ACID properties needed for a high-performance filesystem.
Idea: Use a database engine (Postgres, MariaDB) on raw partitions with a fast separate nVME log file; build POSIX file system semantics on top. It's pretty obvious that this could work; I'm just starting to implement it so performance and durability can be measured.
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