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Re: Hot standby having high requested checkpoints?



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@xxxxxxxxxxxxxxxxxxx>  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?





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