Re: Could synchronous streaming replication really degrade the performance of the primary?

From: "Merlin Moncure" <mmoncure(at)gmail(dot)com>
> On Wed, May 9, 2012 at 8:06 AM, MauMau <maumau307(at)gmail(dot)com> wrote:
>> Hello,
>>
>> I've heard from some people that synchronous streaming replication has
>> severe performance impact on the primary. They said that the transaction
>> throughput of TPC-C like benchmark (perhaps DBT-2) decreased by 50%. I'm
>> sorry I haven't asked them about their testing environment, because they
>> just gave me their experience. They think that this result is much worse
>> than some commercial database.
>
> I can't speak for other databases, but it's only natural to assume
> that tps must drop. At minimum, you have to add the latency of
> communication and remote sync operation to your transaction time. For
> very short transactions this adds up to a lot of extra work relative
> to the transaction itself.

Yes, I understand it is natural for the response time of each transaction to
double or more. But I think the throughput drop would be amortized among
multiple simultaneous transactions. So, 50% throughput decrease seems
unreasonable.

If this thinking is correct, and some could kindly share his/her past
performance evaluation results (ideally of DBT-2), I want to say to my
acquaintance "hey, community people experience better performance, so you
may need to review your configuration."

Regards
MauMau