I’ve used RocksDB for this kind of thing in the past with good results. It’s very thorough from a data corruption detection/rollback perspective (this is naturally much easier to get right with LSMs than B+ trees). The Rust bindings are fine.

It’s worth noting too that B+ tree databases are not a fantastic match for ZFS - they usually require extra tuning (block sizes, other stuff like how WAL commits work) to get performance comparable to XFS/ext4. LSMs on the other hand naturally fit ZFS’s CoW internals like a glove.