On Mon, Apr 19, 2010 at 9:23 PM, Bruce Momjian <bruce@momjian.us> wrote:
> Robert Haas wrote:
>> > Well, the point is that you are getting it for _unusual_ circumstances.
>> > Seems it is only when you are getting it for typical workloads that it
>> > should be increased.
>>
>> I guess. I am not sure we should consider "doing a large CTAS" to be
>> an unusual workload, though. Sure, most of us don't do that every
>> day, but what do we get out of having it be slow when we do decide to
>> do it? Up until today, I had never heard anyone say that there was
>> any possible performance trade-off, and...
>>
>> > However, this is the first time I am hearing that
>> > battery-backed cache favors the default value.
>>
>> ...if that's as bad as it gets, I'm still not sure we shouldn't
>> increase the default. Most people will not have their first
>> experience of PG on a server with a battery-backed RAID controller,
>> I'm thinking. And people who do have battery-backed RAID controllers
>> can tune the value down if need be. I have never yet heard anyone
>> justify why all the values in postgresql.conf should be defined as
>> "the lowest value that works best for at least 1 user".
>>
>> Then again, I don't really know what I'm talking about. I think we
>> should be listening very carefully to people who have spent a lot of
>> time tuning this and taking their advice on how it should be set by
>> default.
>
> The current default was just chosen to reduce the PG disk footprint. It
> probably should be increased, unless we find that the smaller working
> set is a win in many cases.
Yeah. 48MB is not much these days.
...Robert