[Exim] On fsync() in Exim

Hello,

I observe sometimes a high number of disk transactions with a low values
of throughput, which made me wonder about fsync(). I noticed that
there is also fdatasync(), which only updates data but not metadata and
wondered if that might help. Has it been tried? Are there places in
the code where it could be used?

Does anybody run Exim with fsync() replaced by a no-op? My uptimes are
bound by upgrades and I didn't have a crash during the last year for sure,
so I wonder if fsync() is worth the efforts for me.

Michael