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From: Jamie Lokier <jamie@shareable.org>
Subject: Re: [Qemu-devel] Re: [PATCH][v2] Align file accesses with cache=off
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To: qemu-devel@nongnu.org

Anthony Liguori wrote:
> >If you change part of the data but leave the checksum as-is, you'd 
> >hopefully get a checksum mismatch... ;)
> 
> That's the point though, you're not changing part of the data.  You're 
> rewriting the same data.

Usually you're changing some bytes in a block but leaving others the same.
Why else would you write at all?

But even if you do write the same bits _exactly_, the bits written
will not overlay the original data bits precisely enough to make
aborting in the middle seamless.

-- Jamie