On Wed, Jan 13, 2016 at 11:51 AM, Jeff Janes <jeff.ja...@gmail.com> wrote:

> Anyway, it looks to me like you have a checkpoint problem.  The checkpoint
> overwhelms your IO system.  The overwhelmed IO system then backs up into
> the bgwriter.  What you see in the bgwriter is just a symptom, not the
> cause.  The background writer is usually not very useful in recent versions
> of PostgreSQL, anyway.  But, the same IO problem that is clogging up the
> background writer is also clogging up either your buffer_backend, or your
> WAL writes/fsyncs.  And both of those will destroy your throughput.
>

That was my intuition too. Not enough I/O available from the hardware for
the workload requested.

As recommended, log your checkpoints and try tuning them to spread the load.

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