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Date:      Wed, 21 Apr 2004 13:47:43 -0700 (PDT)
From:      Julian Elischer <julian@elischer.org>
To:        Garance A Drosihn <drosih@rpi.edu>
Cc:        hackers@freebsd.org
Subject:   Re: how to flush out cache.?
Message-ID:  <Pine.BSF.4.21.0404211346500.31770-100000@InterJet.elischer.org>
In-Reply-To: <p0602041cbcac8b3862c2@[128.113.24.47]>

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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@gilead.netel.rpi.edu
> Senior Systems Programmer           or  gad@freebsd.org
> Rensselaer Polytechnic Institute    or  drosih@rpi.edu
> 



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