Message-ID: <43FE1110.1030707@vilain.net>
Date: Fri, 24 Feb 2006 08:46:24 +1300
From: Sam Vilain <sam@vilain.net>
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To: "Theodore Ts'o" <tytso@mit.edu>
Cc: Xin Zhao <uszhaoxin@gmail.com>, Arjan van de Ven <arjan@infradead.org>,
       linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: Re: question about possibility of data loss in Ext2/3 file system
References: <4ae3c140602221356x15015171h5aa4a3d7bb6034e0@mail.gmail.com> <1140645651.2979.79.camel@laptopd505.fenrus.org> <4ae3c140602221434v6ec583a7yf04df5fa7a4948fc@mail.gmail.com> <20060223045836.GC9645@thunk.org>
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Theodore Ts'o wrote:
>>Also, the scheme you mentioned is just for new file creation. What
>>will happen if I want to update an existing file? Say, I open file A,
>>seek to offset 5000, write 4096 bytes, and then close. Do you know how
>>ext2/3 handle this situation?
> If you have a power failure right after the close, the data could be
> lost.  This is true for pretty much all Unix filesystems, for
> performance reasons.  If you care about the data hitting disk, the
> application must use fsync().  

I always liked Sun's approach to this in Online Disk Suite - journal at 
the block device level rather than the FS / application level. 
Something I haven't seen from the Linux md-utils or DM.

Sam.
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