From: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com> |
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To: | MauMau <maumau307(at)gmail(dot)com> |
Cc: | Claudio Freire <klaussfreire(at)gmail(dot)com>, Merlin Moncure <mmoncure(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Could synchronous streaming replication really degrade the performance of the primary? |
Date: | 2012-05-10 18:02:57 |
Message-ID: | CAHGQGwESM47xbuc+d-WPUGyFzoSk2sQ3uWN2cVQpXUC_qyQeKA@mail.gmail.com |
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Lists: | pgsql-performance |
On Thu, May 10, 2012 at 8:34 PM, MauMau <maumau307(at)gmail(dot)com> wrote:
> Today, they told me that they ran the test on two virtual machines on a
> single physical machine. They also used pgpool-II in both cases. In
> addition, they may have ran the applications and pgpool-II on the same
> virtual machine as the database server.
So they compared the throughput of one server running on a single machine
(non replication case) with that of two servers (i.e., master and
standby) running
on the same single machine (sync rep case)? The amount of CPU/Mem/IO
resource available per server is not the same between those two cases. So
ISTM it's very unfair for sync rep case. In this situation, I'm not
surprised if I
see 50% performance degradation in sync rep case.
> It sounded to me that the resource is so scarce that concurrency was low, or
> your assumption may be correct. I'll hear more about their environment from
> them.
>
> BTW it's pity that I cannot find any case study of performance of the
> flagship feature of PostgreSQL 9.0/9.1, streaming replication...
Though I cannot show the detail for some reasons, as far as I measured
the performance overhead of sync rep by using pgbench, the overhead of
throughput was less than 10%. When measuring sync rep, I used two
set of physical machine and storage for the master and standby, and
used 1Gbps network between them.
Regards,
--
Fujii Masao
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