From: Brian Fehrle <brianf@consistentstate.com>
To: pgsql-admin@postgresql.org
Subject: Re: Hot standby having high requested checkpoints?
Date: Thu, 08 Mar 2012 15:16:01 -0700
Message-ID: <4F592FA1.6060005@consistentstate.com> (raw)
In-Reply-To: <4F500868.8060603@consistentstate.com>
References: <4F4D5AE0.9020204@consistentstate.com>
<CA+U5nMKcy_wkzJdpwsjyaa76ucyw0FkDhdXnMCypbAwPF0JSEQ@mail.gmail.com>
<4F500868.8060603@consistentstate.com>
Anyone have any thoughts on why this may be happening?
thanks,
- Brian F
On 03/01/2012 04:38 PM, Brian Fehrle wrote:
> I just now ran the following query a few times after each other on the
> hot standby:
>
> select now(), * from pg_stat_bgwriter;
>
> Here are the results:
>
> now | checkpoints_timed | checkpoints_req |
> buffers_checkpoint | buffers_clean | maxwritten_clean |
> buffers_backend | buffers_alloc
> -------------------------------+-------------------+-----------------+--------------------+---------------+------------------+-----------------+---------------
>
> 2012-03-01 23:24:49.099194+00 | 11546 | 145300
> | 1000409459 | 38483026 | 170724 |
> 5058186 | 438703950
> 2012-03-01 23:24:52.139176+00 | 11546 | 145300
> | 1000409459 | 38483027 | 170724 |
> 5058191 | 438703975
> 2012-03-01 23:24:59.129171+00 | 11546 | 145302
> | 1000409459 | 38483081 | 170724 |
> 5058214 | 438704438
> 2012-03-01 23:25:05.957532+00 | 11546 | 145304
> | 1000409459 | 38483118 | 170724 |
> 5058230 | 438704689
> 2012-03-01 23:25:09.519175+00 | 11546 | 145305
> | 1000409459 | 38483160 | 170724 |
> 5058239 | 438704968
> 2012-03-01 23:25:37.019194+00 | 11546 | 145308
> | 1000409459 | 38483259 | 170724 |
> 5058255 | 438705566
> 2012-03-01 23:25:40.659164+00 | 11546 | 145308
> | 1000409459 | 38483268 | 170724 |
> 5058257 | 438705639
> 2012-03-01 23:25:47.239281+00 | 11546 | 145309
> | 1000409459 | 38483283 | 170724 |
> 5058266 | 438705815
> 2012-03-01 23:26:23.858716+00 | 11546 | 145312
> | 1000409459 | 38483393 | 170724 |
> 5058307 | 438706561
> 2012-03-01 23:26:46.467493+00 | 11546 | 145317
> | 1000409670 | 38483524 | 170724 |
> 5058354 | 438707619
>
> in two minutes, I saw 17 checkpoints_req, and the number of
> buffers_checkpoint didn't budge till the last few and even then not much.
>
> checkpoint_segments = 256
>
> - Brian F
>
> On 03/01/2012 01:35 AM, Simon Riggs wrote:
>> On Tue, Feb 28, 2012 at 10:53 PM, Brian Fehrle
>> <brianf@consistentstate.com> wrote:
>>
>>> I have two PostgreSQL 9.0.5 clusters, one is a master and the other
>>> is a hot
>>> standby via streaming replication. I'm monitoring some stats on each
>>> and I'm
>>> noticing something very odd. On the master, I get between 2 and 4
>>> requested
>>> checkpoints per hour, but on the hot standby I'm seeing between 200
>>> and 300
>>> requested checkpoints per hour.
>> We don't do a restartpoint on the standby unless we see a checkpoint
>> record, so that result should be impossible.
>>
>> So I'm guessing you're reading the stats wrong?
>>
>
>
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-admin@postgresql.org
Cc: brianf@consistentstate.com
Subject: Re: Hot standby having high requested checkpoints?
In-Reply-To: <4F592FA1.6060005@consistentstate.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox