fsync is rarely truly durable in the sense the article describes. it does help with loss ordering in a lot of cases, and flushes often do some work, but true durability, the idea that after fsync there will not be any rollback or tail loss unless there's catastrophic failure, sorry, nope. everyone in the chain ends up in the hot path being the hotspot, then they break it because y'all are addicted to spamming syncs then they move it to a new api, then slowly the syncs come back on the new api, then everyone moves again layer by layer. somewhat common examples in recent years are nvme vendors who implement nvme flush in terms of just pushing the write cache down, but won't always also finalize and flush in flight or scheduled ftl operations due to the insane worst case latency costs associated. weren't apple also caught doing the same in recent years, in part because their ftl shared memory, bus and privilege with the higher exception levels? there's also the rumors people say about enterprise drives being better here, but not doing so is even a saleable product in those environments: https://www.atpinc.com/technology/ssd-flush-cache-technology and some other vendors just have arbitrary firmware patches to compete (that is: you could buy "enterprise grade" hardware second hand and be entirely unaware of the actual command behavior).