Re: Improvement of checkpoint IO scheduler for stable transaction responses

On Wed, Jul 17, 2013 at 2:54 PM, Amit Kapila <amit(dot)kapila(at)huawei(dot)com> wrote:
> I think Oracle also use similar concept for making writes efficient, and
> they have patent also for this technology which you can find at below link:
> http://www.google.com/patents/US7194589?dq=645987&hl=en&sa=X&ei=kn7mUZ-PIsWq
> rAe99oDgBw&sqi=2&pjf=1&ved=0CEcQ6AEwAw
>
> Although Oracle has different concept for performing checkpoint writes, but
> I thought of sharing the above link with you, so that unknowingly we should
> not go into wrong path.
>
> AFAIK instead of depending on OS buffers, they use direct I/O and infact in
> the patent above they are using temporary buffer (Claim 3) to sort the
> writes which is not the same idea as far as I can understand by reading
> above thread.

They are not even sorting anything, the patent is for
opportunistically looking for adjacent dirty blocks when writing out a
dirty buffer to disk. While a useful technique, this has nothing to do
with sorting checkpoints. It's also a good example why the patent
system is stupid. It's an obvious idea that probably has loads of
prior art. I'm no patent lawyer, but the patent also looks like it
would be easy to bypass by doing the equivalent thing in a slightly
different way.

Regards,
Ants Aasma
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