From: utzoo!decvax!cca!gwyn@Brl@sri-unix
Newsgroups: net.unix-wizards
Title: Re:  dump and restor
Article-I.D.: sri-unix.4277
Posted: Sun Nov 21 03:52:08 1982
Received: Mon Nov 22 03:48:46 1982

From:     Doug Gwyn <gwyn@Brl>
Date:     17 Nov 82 11:31:39-EST (Wed)
The idea of the System III dump recommendation is to minimize the number
of dump tapes while permitting recovery from an unreadable "daily"
backup.  In fact dump levels 2..8 are intended to be used but only
after the scheme has been running for some time.
Basically,
LEVEL 0
	LEVEL 9 (Hanoi)
	LEVEL 9
	LEVEL 9
	LEVEL 9 nearly full
  LEVEL 1
	LEVEL 9 nearly empty
	LEVEL 9
	LEVEL 9
	LEVEL 9 nearly full
    LEVEL 2
	LEVEL 9 nearly empty
 ...
>From my experience with tape dumps I would say that this is a nice
scheme, but its bookkeeping is trickier than the daily/weekly/monthly/...
scheme even though it uses fewer tapes.

I would add the recommendation that one always have TWO copies of
a "baseline" dump (such as levels 0, 1, 2... above) since Murphy's law
seems to apply to magtapes with a vengeance.