On Monday 11 May 2009, Dustin J. Mitchell wrote:
>On Thu, Mar 5, 2009 at 10:32 PM, Uwe Menges <uwe.menges AT web DOT de> wrote:
>> Another quick check with "ls -l /proc/`pidof taper`/fd/" showed me it was
>> really true, the taper was happily reading its own amanda-split-buffer-*
>> files (marked as (deleted) but it nevertheless had the file handles),
>> writing them again as amanda-split-buffer-* files...
>
>Now that I've been over this code several times with a
>fine-toothed-comb (I've rewritten it to use Perl and the transfer
>architecture), I can't figure out what happened here.  It makes sense
>that the *taper* was reading and writing from its split-buffer files
>-- that's what they're for!  If *gnutar* were reading the split files,
>there would be a problem, since those files are created with mkstemp
>and immediately unlinked.
>
>Dustin

This walks and talks like another duck I believe I've seen on lkml, Dustin.

There has been an ongoing discussion on lkml regarding the nearly required use 
of the fsync operator on ext3-4 systems if absolute data integrity is needed.  
Otherwise the 5 second rule, with no locking used to force synchronization, 
can find a file on the drive that has not been actually unlinked on the 
platter surface, or some such tom-foolery I don't fully grok all the nuances 
of.  I don't believe I have been a victim of that, but the discussion has been 
hot & heavy at times about how to speed up such ops without forcing software 
to use the fsync function and therefore suffering a slowdown since fsync seems 
to be an expensive operation in that it bypasses the schedulers ability to 
efficiently manage disk accesses by forcing an out of order (seek wise) flush 
of all dirty buffers held.  At least that is what I have gotten out of trying 
to follow the thread so far.  Theo. Tso can probably shed more light, far more 
clearly than I on this.

-- 
Cheers, Gene
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