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Date:      Mon, 14 Oct 2013 13:39:53 +0100
From:      RW <rwmaillists@googlemail.com>
To:        freebsd-questions@freebsd.org
Subject:   Re: SU+J Lost files after a power failure
Message-ID:  <20131014133953.58f74659@gumby.homeunix.com>
In-Reply-To: <l3gc7e$c91$1@ger.gmane.org>
References:  <525A6831.5070402@gmail.com> <l3gc7e$c91$1@ger.gmane.org>

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On Mon, 14 Oct 2013 05:02:22 -0400
Michael Powell wrote:

> David Demelier wrote:
> 
> > Hello there,
> > 
> > I'm writing because after a power failure I was unable to log in on
> > my FreeBSD 9.2-RELEASE. The SU+J journal were executed correctly
> > but some files disappeared, including /etc/pwd.db. Thus I was
> > unable to log in.
> > 
> > I've been able to regenerate the password database with a live cd
> > but I'm afraid that more files had disappeared somewhere else...
> > 
> > I think this is a serious issue, the journal should not truncate
> > files, so something should have gone wrong somewhere..

The journalling in  SU+J has nothing to do with data integrity.

When the system isn't shut-down cleanly, soft-updates are supposed to
leave the filesystem in a self-consistent state, except that it may
lose track of some freed disk space. The journal allows that space to
be recovered without the lengthy background fsck that used to cripple
performance.

If you are having problems with data integrity you might try gjournal or
zfs instead. If you look back at the lists before these were added
there was a lot of suspicion about soft-updates and background checks.
Some of the problems were explained by some (mostly desktop) drives
incorrecty reporting what has been commited to disk - I don't know
whether this is still the case.


> This error about the replay of the journal(s) failing is somewhat 
> disconcerting. 

I think this is probably a good thing. With background checks you would
(if you were looking) occasionally see "unexpected soft-update
inconsistency" during the background check, which would lead to a
foreground check on the next boot.






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