It wasn't ext4 that introduced a paradigm shift but ext3: the fsync() implementation in ext3 by design wrote all buffered writes for the whole filesystem, not

It wasn't ext4 that introduced a paradigm shift but ext3: the fsync() implementation in ext3 by design wrote all buffered writes for the whole filesystem, not just a single file, hence it was so horribly slow that it taught a generation of application programmers never to call fsync() to avoid multi-second pauses.