Strange case of deleting lots of files and "df" not recognizing it....(unless I umount/mount) the disk...

[Ben Myers]

On Mon, Jun 25, 2012 at 09:02:11AM +0200, Emmanuel Florac wrote:
> Le Sun, 24 Jun 2012 22:58:12 -0700 vous écriviez:
> 
> > So when does it actually synchronize w/o me forcing it?  (I.e.
> > umount/mount)?
> > 
> 
> Yes, it happens sometimes and a umount/mount is needed to fix it.

You may find that this will get the job done:
echo 3 > /proc/sys/vm/drop_caches

-Ben