From: Craig James <craig_james@emolecules.com>
To: Scott Marlowe <scott.marlowe@gmail.com>
Cc: pgsql-admin@postgresql.org
Subject: Re: Who is causing all this i/o?
Date: Fri, 20 May 2011 16:41:05 -0700
Message-ID: <4DD6FC11.4000706@emolecules.com> (raw)
In-Reply-To: <BANLkTikJ6xn-pKRhRA1HGiNotQt7N=1QDQ@mail.gmail.com>
References: <4DD6D9A6.1010101@emolecules.com>
<BANLkTikJ6xn-pKRhRA1HGiNotQt7N=1QDQ@mail.gmail.com>
On 5/20/11 4:25 PM, Scott Marlowe wrote:
> On Fri, May 20, 2011 at 3:14 PM, Craig James<craig_james@emolecules.com> wrote:
>> Our development server (PG 8.4.4 on Ubuntu server) is constantly doing
>> something, and I can't figure out what. The two production servers, which
>> are essentially identical, don't show these symptoms. In a nutshell, it's
>> showing 10K blocks per second of data going out, all the time, and
>> essentially zero blocks per second of input.
>> After a lot of digging around, I found this in the /postgres/pg_stat_tmp
>> directory. If I list the directory including the i-nodes once every second,
>> I find that a new 2MB file is being created roughly once every two seconds:
> Have you got a lot of databases in your development environment? I
> think that can sometimes cause a lot of pg_stat writes.
Yes. The production servers have a dozen or so databases, but the development server has a couple hundred databases. Does that count as "a lot of databases"?
We've had even more databases in the past (>500) and didn't see this sort of I/O activity.
The odd thing is that this activity is gradually growing, so slowly that you don't notice it right away. A month or two ago, nothing. A couple weeks ago, a constant stream of "grass" in xload's graph. Today, xload is showing a 50% all the time. I can only guess that the load will continue to increase.
Is there a way to tell Postgres not to do this, or to do it less? It's not a big disaster (yet), but it's annoying to have the system spewing a couple megabytes of pg_stat_tmp data every few seconds.
Thanks,
Craig
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To: pgsql-admin@postgresql.org
Cc: craig_james@emolecules.com, scott.marlowe@gmail.com
Subject: Re: Who is causing all this i/o?
In-Reply-To: <4DD6FC11.4000706@emolecules.com>
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