Re: fsync and hardware write cache

pgsql(at)mohawksoft(dot)com writes:

> Something to think about:
>
> if you run PostgreSQL with fsync on, but you use the hardware write cache
> on your disk drives, how likely are you to lose data? Obviously, this is a
> fairly limited problem, as it only applies to power down (which you can
> control) or power loss where the risks may be reduced but not eliminated
> with a UPS.
>
> Does it make sense to add a platform specific call that will flush a write
> cache when fsync is enable?

AIUI, recent versions of the Linux kernel are supposed to do this for
you, but not all drives honor the "flush" command, so you're still at
the mercy of your disk vendor...

-Doug
--
Let us cross over the river, and rest under the shade of the trees.
--T. J. Jackson, 1863