Robert Haas <robertmh...@gmail.com> wrote: > I also think Bruce's idea of calling fsync() on each relation just > *before* we start writing the pages from that relation might have > some merit. What bothers me about that is that you may have a lot of the same dirty pages in the OS cache as the PostgreSQL cache, and you've just ensured that the OS will write those *twice*. I'm pretty sure that the reason the aggressive background writer settings we use have not caused any noticeable increase in OS disk writes is that many PostgreSQL writes of the same buffer keep an OS buffer page from becoming stale enough to get flushed until PostgreSQL writes to it taper off. Calling fsync() right before doing "one last push" of the data could be really pessimal for some workloads. -Kevin
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