Re: postgresql.conf recommendations

"ac(at)hsk(dot)hk" <ac(at)hsk(dot)hk> wrote:
> Johnny Tan <johnnydtan(at)gmail(dot)com> wrote:

>>shared_buffers = 48GB# min 128kB

> From the postgresql.conf, I can see that the shared_buffers is
> set to 48GB which is not small,  it would be possible that the
> large buffer cache could be "dirty", when a checkpoint starts, it
> would cause a checkpoint I/O spike.
>
>
> I would like to suggest you about using pgtune to get recommended
> conf for postgresql.

I have seen symptoms like those described which were the result of
too many dirty pages accumulating inside PostgreSQL shared_buffers.
It might be something else entirely in this case, but it would at
least be worth trying a reduced shared_buffers setting combined
with more aggressive bgwriter settings.  I might try something like
the following changes, as an experiment:

shared_buffers = 8GB
bgwriter_lru_maxpages = 1000
bgwriter_lru_multiplier = 4

-Kevin