Re: Duplicating 5 tapes takes 6?????

[PaulMmn <PaulMmn@xxxxxxxxxxxxx>]

I know it's been over a month, but I'm just catching up on some email...

Not all tapes are the same length; the 1000' (example) tape in a 
cartridge is probably +/-  X% due to manufacturing tolerances (or a 
manufacturer trying to save a foot or so of tape here and there).  So 
original #1 may hold more data than duplicate #1, and so on.

You'll could end up with a piece of the data from tape #1 on dupe #2; 
a bigger piece from tape #2 on dupe#3, and so on.  If your original 
save used almost all of tape #5, some of the data would get pushed 
onto tape #6.

That's why you can't just duplicate each tape separately-- DUPTAP has 
to read the entire set in sequence as it creates the duplicate on 
another drive.

You can check this out-- do a DSPTAP of all tapes from both sets and 
count the data blocks on the original set and the duplicate set.  The 
totals should match.

--Paul E Musselman
PaulMmn@xxxxxxxxxxxxxxxxxxxx


> We have the 3570 tape library.  Our full system save takes 5 tapes.  After
> the last full save, I used the DUPTAP command like always to make a
> duplicate copy.  I ended up needing 6 tapes for the duplication.
>
> Anybody seen this before?  How/why would six tapes be used when duplicating
> 5?
>
> Note: BRMS is not used.
>
> Thanks,
> Charles