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Re: Calling Customer Service for bad sectors

    Date: Sat, 26 Nov 88 23:33 EST
    From: RWK@F.ILA.Dialnet.Symbolics.COM (Robert W. Kerns)

	Date: Tue, 22 Nov 88 09:29 EST
	From: Reti@WESER.sreti.symbolics.com (Kalman Reti)
					      Compared to hours for restoring the
	    LMFS, not counting down time waiting for customer service.
	But what about the hours lost due to corrupted files, missing data, etc.
	if you are wrong about the 20 second fix?

    Well, are you talking about the corrupted files, missing data, etc. if
    you are wrong about DOING the 20 second fix, or NOT DOING the 20 second
I meant if the 20 second fix increases the damage to the file system instead
of decreasing it.
	  I've seen a lot of problems from doing a full LMFS restore.
    Sometimes some of the backup tapes turn out bad.  
I have an iron-clad rule: compare all backup tapes after writing them, preferably
on another drive.  The only time I've personally had a backup tape turn out to
be bad is when I haven't followed that rule.  I suppose it is also possible
that the medium could go bad, in which case you should write TWO backup tapes.
This hasn't ever happened to me (except for one 7-year-old dectape that got pretty
dirty in the trunk of my car).
						      And there's always
    some files that were written AFTER the most recent backup, and you'll
    find those out by stumbling into bugs and things that you already fixed
    a week ago.

    If there's a simple fix, it's worth a lot.  It's even worth spending a
    somewhat larger block of time than doing a full restore, because the
    results are better and more reliable.  If you do a full restore, and one
    of the important tapes is bad, you're SCREWED.
I guess this means we should have a tool for really reading a backup tape
(instead of just the header information), to ensure before you do a restore
that you can get all the bits off and that those bits look like LMFS files.
Such a tool isn't hard to write, I'll add it to my queue of things to do
in my spare time.