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Date: Mon, 1 May 1995 12:03:40 -0600
From: Nate Williams <nate@trout.sri.MT.net>
Message-Id: <199505011803.MAA01024@trout.sri.MT.net>
In-Reply-To: Poul-Henning Kamp <phk@ref.tfs.com>
       "Re: Compress dumps?" (May  1, 10:49am)
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To: Poul-Henning Kamp <phk@ref.tfs.com>, terry@cs.weber.edu (Terry Lambert)
Subject: Re: Compress dumps?
Cc: obrien@leonardo.net, hackers@FreeBSD.org
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> > I always want to cry when someone suggests stream compression on
> > dump formats.
> 
> Terry,
> 
> In my 10+ years in computing, I have >once< had a chance to restore
> from a damaged media which were still partially readable. 

In my 10+ years in computing, I have had *multiple chances (experiences)
trying to resurrect a dump from damaged media.  I can count on the my
fingers the # of restores I've had to do which were bad, but it's not an
experience I'd go through again if I had a choice.

> Comparing that to how many tapes I've written, streams based compression
> is a very low risk thing to do to save money.

Compared to how many tapes I've written and how many went bad, I would
*NEVER* do stream based compression.  Note, my experience has been that
the failure rate is not very high, but for the cost of a few tapes the
cost of *my* time to get the backup (if possible) and the cost of lost
work of the developers it isn't an issue.

> How about this observation btw:
> 
> If I can compress at least 3:1, I can make two copies, and still save
> 33% on media... (Assuming you fill them of course).

The price of backup media has never been an issue for me.  If price is
an issue for you, then rotate your tapes.


Nate