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Date: Mon, 14 Oct 2013 14:51:55 -0400 (EDT)
From: Daniel Feenberg <feenberg@nber.org>
To: Bruce Cran <bruce@cran.org.uk>
Subject: Re: SU+J Lost files after a power failure
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Cc: David Demelier <demelier.david@gmail.com>,
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On Mon, 14 Oct 2013, Bruce Cran wrote:

> On 10/14/2013 6:16 PM, CeDeROM wrote:
>> Isn't there Journal to prevent and reverse such damage?
>
> Unlike other journaling filesystems, UFS+J only protects the metadata, not 
> the data itself - i.e. I think it ensures you won't have to run a manual 
> fsck, but just like plain old UFS files may be truncated as the journal is 
> replayed.

This discussion skirts the critical issue - are files that are not open 
for writing endangered? No description of the uses of journaling can be 
considered informative if it doesn't address that explicitly. As a naive 
user I have always assumed that once closed, a file was invulnerable to 
improper shutdowns, but this discussion shakes that belief.

I expect the answer may be different for SSD and spinning disks.

dan feenberg