Scott Carey wrote:
> the OS can either quickly allocate to the process or
> the page cache from the free buffers, or more slowly take from the page
> cache, or even more slowly page out a process page.
>
Aha, now it all makes sense.
> I like to use the '5 second rule'. dirty_background_ratio should be sized
> so that it takes about 5 seconds to flush to disk in optimal conditions.
> dirty_ratio should be 2x to 5x this depending on your application's needs --
> for a system with well tuned postgres checkpoints, smaller tends to be
> better to limit stalls while waiting for the checkpoint fsync to finish.
>
Thanks a lot, this is invaluable information.
Regards,
Mike