Re: Database performs massive reads when I'm doing writes.

It is Postmaster itself:
11068 - 315.9M 136K 0K 85% postmaster
11000 - 56808K 8K 0K 15% postmaster
11003 - 0K 80K 0K 0% postmaster
11004 - 0K 24K 0K 0% postmaster
11067 - 0K 0K 0K 0% load_rets.py

The above are the atop lines for just postmaster. This is a 10s snapshot so you can see lots of read activity.
The load_rets.py task is the Python script loading the database.

--Ray

----- Original Message -----

> From: "Jeff Janes" <jeff(dot)janes(at)gmail(dot)com>
> To: "Ray Cote" <rgacote(at)appropriatesolutions(dot)com>
> Cc: pgsql-general(at)postgresql(dot)org
> Sent: Thursday, June 6, 2013 4:05:28 PM
> Subject: Re: [GENERAL] Database performs massive reads when I'm doing
> writes.

> On Thu, Jun 6, 2013 at 9:53 AM, Ray Cote <
> rgacote(at)appropriatesolutions(dot)com > wrote:

> > Hello:
>

> > I have a PostgreSQL 9.0.3 database that has suddenly started
> > exhibiting odd read behavior.
>

> > The version number is:
>
> > "PostgreSQL 9.0.3 on x86_64-unknown-linux-gnu, compiled by GCC gcc
> > (GCC) 4.1.2 20080704 (Red Hat 4.1.2-50), 64-bit"
>
> > This was compiled from source about a year ago and has been running
> > just fine.
>
> > The database feeds a very low-volume web site (a few hits per
> > minute).
>

> > Starting a few days ago we started to see a strange behavior where
> > writing to the database causes massive read operations.
>
> > For example, I have a table that needs to be updated every night
> > (about 20,000 rows).
>
> > Using Django ORM, we update them one item at a time.
>
> > Usually the overall process takes a few minutes; it is now taking
> > hours (like over 15 hours).
>

> > Running atop, we're seeing Read Disk values in the range of
> > 147.2M/10s and Write Disk values in the range of 16K/10s.
>
> > Together, the Disk throughput is in the high 90% and frequently
> > hits
> > 100%.
>

> Which specific processes are using the disk? (on my atop, if I hit
> 'c' it will change mode to show me the entire so-called "command
> line", which will let you know if the culprit is a vacuum worker,
> the checkpointer, or someone else).

> Cheers,

> Jeff
--

Ray Cote, President Appropriate Solutions, Inc.
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www.AppropriateSolutions.com 603.924.6079