On 2011-08-04 08:58, DongJin Lee wrote: > just adding 2c question: > >> On Thu, Aug 4, 2011 at 18:45, Jens Axboe <jaxboe@xxxxxxxxxxxx> wrote: >> That does not mean it's stable, it could just be >> sitting in the drive write back cache. > > right, example with a simple hdd 2tb with some 64mb cache, so indeed, > there's no real way to confirm that the data has been physically > written to the mechanical platter; Usually any type of device that has a write back caching scheme also supports a command to sync/flush that cache. This is what the kernel does when you use one of the fsync() variants. > but as I understand when shutting down the system, all are physically > written to the platter; so I wonder what command the os issues to the > disk then? maybe just unmount do so? The devices are stopped at some point, that should ensure that the caches are stable. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
