The “guarantees” that existing filesystems make with regard to persistence
in the face of a system crash was the subject of a session led by Amir
Goldstein at the 2019 Linux Storage, Filesystem, and Memory-Management
Summit (LSFMM). The problem is that filesystem developers are not willing
to make much in the way of guarantees unless applications call fsync()—something
that is not popular with application developers, who want a cheaper option.

Source: LWN.net – [$] Filesystems and crash resistance