Re: strange performance regression between 7.4 and 8.1

Florian Weimer wrote:
> * Alex Deucher:
>
>
>> I have noticed a strange performance regression and I'm at a loss as
>> to what's happening.  We have a fairly large database (~16 GB).
>>
>
> Sorry for asking, but is this a typo?  Do you mean 16 *TB* instead of
> 16 *GB*?
>
> If it's really 16 GB, you should check if it's cheaper to buy more RAM
> than to fiddle with the existing infrastructure.
>

This brings me to a related question:

Do I need to specifically configure something to take advantage of
such increase of RAM?

In particular, is the amount of things that postgres can do with RAM
limited by the amount of shared_buffers or some other parameter?
Should shared_buffers be a fixed fraction of the total amount of
physical RAM, or should it be the total amount minus half a gigabyte
or so?

As an example, if one upgrades a host from 1GB to 4GB, what would
be the right thing to do in the configuration, assuming 8.1 or 8.2?  (at
least what would be the critical aspects?)

Thanks,

Carlos
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