Checkpoint and Background Writer Statistics

Hi, list.

We're trying to pull a few various metrics from the postgres catalogs to
analyze database performance, and included is buffers_checkpoint and
buffers_clean from pg_stat_bgwriter.

One of our clients has an lru_max_dirty setting of 1000 and a bgwriter_delay
of 200, but we're still seeing much higher growth in the buffers_checkpoint
than buffers_clean, with buffers_checkpoint increasing at about 20 times the
rate that buffers_clean is. We don't see very much growth in the
maxwritten_clean, though - something like one every couple of days.

So the questions is, why are there still so many more checkpoint buffers
than clean buffers written? Does the buffers_checkpoint value include more
than we think? If not, can we tune things further?

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Samuel Nelson
Consistent State
www.consistentstate.com
303-955-0509
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