Re: O_DSYNC broken on MacOS X?

On tor, 2010-09-30 at 15:07 -0700, Greg Stark wrote:
> > It's too bad there is no cross-platform way to ask what level of
> hardware-syncing is available.
> 
> Why would the user want to ask this? As far as the user is concerned
> either there are only two "levels": synced or not synced. If it's not
> guaranteed to persist after a power failure it's not synced. It
> doesn't matter whether it's in kernel buffers, drive buffers, or
> anywhere else -- they're all the same from the user's point of view --
> they're non-persistent.

Well, it's not really useful, but that's how it works "everywhere".  On
Linux, fsync carries the stuff from the kernel's RAM to the disk
controller's RAM, and then it depends on some hdparm magic or something
what happens next.