how to flush out cache.?

[Julian Elischer]

On Wed, 21 Apr 2004, Garance A Drosihn wrote:

> At 12:23 PM -0700 4/21/04, Julian Elischer wrote:
> >Ok so I have an application where I need to
> >reread a file I have just written to ensure that it went to disk
> >correctly..
> >
> >Other than reading a few GB of data, is there a way to flush
> >out the cache copy of a file I've written?
> >
> >possibilities include:
> >
> >a file flag saying "don't keep a copy after it's written to disk"?
> >a syscall discard_cached_blocks(fd);
> >
> >
> >?
> >any other suggestions?
> >
> >julian
> >(BTW this would be for 4.x initially)
> 
> Hmm.  That means you couldn't use a 'snapshot' to force the
> issue, right?  If you *could* use snapshots, you could close
> the file, snapshot the partition, mount the snapshot, and
> read the file from it's copy in the snapshot-filesystem.

ingenious, but, no we can't do that..
As I mentionned.. someone suggested using 'dump'
to extract the file from raw disk and checksumming that... :-)

> 
> -- 
> Garance Alistair Drosehn            =   gad at gilead.netel.rpi.edu
> Senior Systems Programmer           or  gad at freebsd.org
> Rensselaer Polytechnic Institute    or  drosih at rpi.edu
>