Hanoi Algorithm - (nf)

[acheng at uiucdcs.UUCP]

#N:uiucdcs:13700058:000:1521
uiucdcs!acheng    Aug 18 10:25:00 1984

I am setting up some dump schedules for our machine and want to 
try this famous "Hanoi algorithm" mentioned in the "man dump".
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     Now a short suggestion on how to perform dumps.  Start with
     a full level 0 dump

          dump 0un

     Next, dumps of active file systems are taken on a daily
     basis, using a modified Tower of Hanoi algorithm, with this
     sequence of dump levels:
                       3 2 5 4 7 6 9 8 9 9 ...
     For the daily dumps, a set of 10 tapes per dumped file sys-
     tem is used on a cyclical basis.  Each week, a level 1 dump
     is taken, and the daily Hanoi sequence repeats with 3.  For
     weekly dumps, a set of 5 tapes per dumped file system is
     used, also on a cyclical basis.  Each month, a level 0 dump
     is taken on a set of fresh tapes that is saved forever.
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After studied it for a while, I could not follow the logic.
1) If there is always a level 1 weekly dump, at most 6 daily tapes
are needed.  How come "a set of 10 daily dump tapes"?

2) For a level n dump, it dumps all files modified since the latest
level m dump (m < n; NOT <= n).  So, there is no difference
between the following 2 sequences, is there?

                       3 2 5 4 7 6 9 8 9 9 ...
                       3 3 5 5 7 7 9 9 9 9 ...


Can any earthlings explain this Hanoi algorithm to me?


Albert Cheng
ihnp4!uiucdcs!acheng
acheng%uiuc at csnet.arpa