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From Klaus Trainer <klaus.trai...@web.de>
Subject Re: delayed_commits false
Date Tue, 06 Jul 2010 21:37:50 GMT

---[Sorry for the noise and not properly quoting previously]---


Mikeal, I suspect you mixed up local data consistency and durability...

In fact, I think it's only the durability one of the ACID properties
that's affected. Basically, the only difference that
delayed_commits=true makes is that if there is e.g. a power outage, the
result of write operations that have committed in the last three or so
seconds might be lost.

I know, it's no question that local data consistency and the other
consistency property you refer to as runtime consistency are not
affected by the delayed_commits setting.

Cheers,
Klaus


On Tue, 2010-07-06 at 13:28 -0700, Mikeal Rogers wrote:
> Just for reference, most SQL databases ship with the fsync to their
> log on a
> 1s or longer cycle, it's pretty standard.
> 
> delayed-commits on doesn't reduce durability because the writes to log
> are
> still append-only and can survive invalid writes and crashes and all
> that.
> Also, they don't reduce runtime consistency because the response isn't
> returned until the document is available. All they do is give the
> client a
> *different* consistency guarantee (available rather than persisted to
> disc).



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