dump level 9

[Alex Zbyslaw]

Jerry McAllister wrote:

>But, I wonder why you chose level 9 for your change dumps.   It sort 
>of defeats the system.   It would be more normal to use level 1.    
>I know that [some much] earlier versions of BSD dump only took levels 
>up to 5, but I presume that since they include up to 9 in the documentation
>it should work.
>  
>
If you only use one level other than 0, then it makes no difference what 
that level is: 1, 9, 5 anything but 0.  A level N dumps everything since 
the last dump < N, which in this case is always the last level 0.

Using "modified tower of hanoi" (so the man page says :-)) can decrease 
the amount of data per dump at the cost of having to do more dumps: e.g. 
I do 0: 1 3 2 1 3 2 ... 0 ...  But if I have to restore everything and 
the last dump was a 2, I have to restore the 0 1 and 2.  Similarly if it 
crashed after 3, I would do 0 1 3.  That cuts down the amount of data 
dumped, but is slightly more complex than just having to restore the 0 
and last 9 (in the OPs case).  I could use 1 7 9, or 4 6 8 instead of 1 
2 3 and the data dumped would be the same in each case.

I was pretty sure that BSD 4.2 had 9 incremental dump levels, but that 
was long, long ago in a universe of 1600bi tapes far, far away :-)

--Alex