High-density drives are usually zoned storage, and it's pretty difficult to implement the regular filesystem API on top of that with any kind of reasonable perf

High-density drives are usually zoned storage, and it's pretty difficult to implement the regular filesystem API on top of that with any kind of reasonable performance (device- vs host- managed SMR). The S3 API can work great on zones, but only because it doesn't let you modify an existing object without rewriting the whole thing, which is an extremely rough tradeoff.