(dump) Hanoi algorithm

[speck at cit-vax.ARPA]

From:  Don Speck <speck at cit-vax.ARPA>

    The reason for keeping two week's worth of daily dump tapes is that
your weekly dump tapes can go bad just when you need them most, forcing
you to substitute the previous week's weekly and daily backups for this
week's ruined weekly tape.  If you don't have daily backups from the
previous week, then you'll lose a week's worth of files if your weekly
tape dies at an inopportune time.  I submit that this is quite likely
to happen, since a tape may write fine but accumulate errors that aren't
noticed until you try to read the tape (i.e, when you NEED to read it).
At least that's what I found yesterday:  20 separate read errors on one
tape.  Fortunately the files I was looking for were elsewhere.

						Don