>> - Filesystems mounted with async,noatime,nodevmtime ("async" is ignored
>>   when you're using soft updates, of course),
>
>On laptops, in addition to this, I also make sure to disable cron
>logging in syslog.conf as otherwise atrun keeps the disk running.
>This is with the atactl setstandby timer set to a few minutes.

I did that, of course; I don't think that causes writes every 5 seconds :-)

FWIW, you really want to set the disk spindown timer much lower; the
research papers on the subject suggested 5-10 seconds was optimal in
terms of power conservation.

--Ken