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Date:      Mon, 6 Oct 1997 04:31:42 +0000 (GMT)
From:      Terry Lambert <tlambert@primenet.com>
To:        ahd@FreeBSD.ORG (Drew Derbyshire)
Cc:        hackers@hub.freebsd.org
Subject:   Re: mount async and possible loss of F/S
Message-ID:  <199710060431.VAA20970@usr09.primenet.com>
In-Reply-To: <199710060106.SAA21602@hub.freebsd.org> from "Drew Derbyshire" at Oct 5, 97 06:06:16 pm

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> The mount command cheerfully states that the async option is not to be used
> unless you are prepared to recreate the file system.    Ummm, exactly 
> what is left so hanging in the wind that you lose the file system rather
> than just the recent updates?

The fsck utility can recover exactly one state transition.  Any more, and
it will return the FS to a "known good state" -- but will it be the
"known good state" the FS was supposed to have been in?

The naser is that if there were 10 transations outstanding, there is only
one known good state.  That means a 1 in 2^10 or 1 in 1024 chance of
getting the "right" "known good state".  Pretty bad odds... but feel
free to gamble; the freedom to gamble is an evolutionary pressure
which promotes the ability to do simple math in the losers.


					Terry Lambert
					terry@lambert.org
---
Any opinions in this posting are my own and not those of my present
or previous employers.



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