Solaris and effective_cache_size

Hi,

There has been some recent discussion on the list about performance
trouble on Solaris.  We have a test environment which includes two
2-way Sun E250s with 2 Gigs of RAM each.  We have experienced some
trouble similar to what others have mentioned, although it has not
been as bad.

I've been investigating some troubles we've been having on one of
those test machines.  When the database gets sort of large, or has
been running for a while, we start to have trouble with performance.
I had a feeling that this might be related to disk caches.

Solaris is _much_ more aggressive about disk caching than Linux is,
it seems.  I suspected that adjusting the effective_cache_size
setting might therefore help.

Using pgbench, I discovered a performance advantage of almost 10% by
increasing the setting from the default 1000 to 1500.  I am not sure
whether this figure will hold up, but it was consistent over multiple
tests.

Has anyone else had any results (similar or different) when playing
with that setting?

Also, does anyone have a good way of testing the random_page_cost?
I've tried to find ways to test this in the past, and I've never had
any luck, because I haven't been able to be sure (in my test) that
the pages are really spread out in a way that the random_page_cost
setting would be tested.

A
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Andrew Sullivan                               87 Mowat Avenue
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