> > Even with true fdatasync it's not obviously good for performance - it takes
> > too long time to write 16Mb files and fills OS buffer cache with trash-:(
>
> True. But at least the write is (hopefully) being done at a
> non-performance-critical time.
So you have non critical time every five minutes ?
Those platforms that don't have fdatasync won't profit anyway.
Even if the IO is done by postmaster the write to the disk has a severe
impact on concurrent other disk activity.
In a real 5 minutes checkpoint setup we are seriously talking about
48 Mb at least, or you risc foreground log creation. On systems I know,
that means 100% busying the disk for at least 8 seconds.
Andreas