something along the lines that the ext3 journal doesn't know what blocks are related to the metadata, so to avoid revealing old data that may be on disk, the filesystem is required to flush all pending writes.
the XFS/ext4 'problem' you refer to is the way every filesystem other than ext3 works. If you don't do a fsync, the data isn't safe and a crash at the wrong time can give you grief.
the functionality that makes this less of a problem on ext3 is the same functionality that makes it behave so horribly when you do a fsync
this is good for crash-prone desktop systems running software that wasn't written to be crash safe (note that it doesn't make the systems safe, it just reduces the probability of data loss)
but if you are running any software that is written to be crash safe, ext3 is about the worst filesystem you could use (in some cases worse than ext2 or other non-journaled filesystem).
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