On Fri, May 16, 2003 at 07:10:20AM -0400, Mitch Collinsworth wrote:
> 
> Taper chunking opens the door to backing up DLEs that are larger than
> a single tape, something which no amount of algo-shuffling is going
> to accomplish.  It also opens the door to allowing taping and dumping
> of a single DLE to proceed in parallel, which can be a huge time-savings
> for large DLEs.  These are both features that a lot of people would like
> to have.  They've also been common deal-breakers for folks looking at
> amanda in the past.

Mitch,
clarify for my your notion of "taper chunking" and the mentioned parallelism.

In your view, if chunking is implemented, it would allow a DLE to be taped
in chunks before the dump had completed.  This would certainly reduce the
maximum size required for some holding disks.  Yet could only be used if
a holding disk were provided.

Do you anticipate the chunks of any specific DLE to be taped sequentially?
I.e. once started, taping only continues for that DLE until completed?
Or do you anticipate interleaving the chunks of multiple DLE's?  I can
forsee difficulty with both approaches compared to only taping when a
dump of a DLE is completed, with chunks for tape spanning of course.

BTW in practice, doesn't the existing parallelism of amanda pretty much
eliminate the time-saving benefits that these proposals might realize?
Taping of completed DLE's goes on while my large DLE's complete and other
DLE's dump while my large DLE's tape.

-- 
Jon H. LaBadie                  jon AT jgcomp DOT com
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