On Thu, Aug 31, 2006 at 08:45:13AM +0200, David Sánchez Martín wrote:
> Hi list:
> 
> I've got a 2 or 3 doubts about amanda and tapes:
> 
> 
> USAGE BY TAPE:
>   Label          Time      Size      %    Nb
>   DIARIO08       0:07  6568933K    3.2     8
> 
> 
> 1.- ¿What does Nb column mean?

I don't know what the "b" stands for, but the column is the 
Number of tape files (i.e. DLEs) written to that tape.
If you were using tape spanning, whereby some DLEs were
split into several pieces, there could be another column,
Nc, Number of Chunks written.

> 
> 2.- ¿Does amanda allways rewinds the tape before writing to it (so tape is
> allways overwrited)? (I think this is true)
> 

Yes.

> 3.- On the other hand, incremental, AFAIK, means "backup of all the files
> that have changed since the last backup, even if that was an incremental
> backup (as opossed to a full backup)". Is there a way to make a differential
> backup ("backup of all the files that have since the last FULL backup").
> 

I don't know of any international standards organization specifying
the meaning of incremental and differential.  Thus, the definitions
are in the eye of the beholder.  Amanda's view does not include
anything called differential.  Its incremental definition is based
on backup levels, an incremental of level X (X == 1 to 9) is the
changes since the last backup of level lower than X.  Because of
the way amanda changes levels (never lower except to level 0 and
only one level higher at a time), that would always be X-1.  So an
incremental of level 4 is the changes since the last level 3.
Not changes since the last backup as the last backup could also
have been a level 4.

-- 
Jon H. LaBadie                  jon AT jgcomp DOT com
 JG Computing
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