Message-ID: <4C191F46.4060408@agliodbs.com>
Date: Wed, 16 Jun 2010 12:00:22 -0700
From: Josh Berkus <josh@agliodbs.com>
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To: pgsql-performance@postgresql.org
Subject: Re: PostgreSQL as a local in-memory cache
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> * fsync=off => 5,100
> * fsync=off and synchronous_commit=off => 5,500

Now, this *is* interesting ... why should synch_commit make a difference
if fsync is off?

Anyone have any ideas?

> tmpfs, WAL on same tmpfs:
> * Default config: 5,200
> * full_page_writes=off => 5,200
> * fsync=off => 5,250
> * synchronous_commit=off => 5,200
> * fsync=off and synchronous_commit=off => 5,450
> * fsync=off and full_page_writes=off => 5,250
> * fsync=off, synchronous_commit=off and full_page_writes=off => 5,500

So, in this test, it seems like having WAL on tmpfs doesn't make a
significant difference for everything == off.

I'll try running some tests on Amazon when I have a chance.  It would be
worthwhile to get figures without Python's "ceiling".

-- 
                                  -- Josh Berkus
                                     PostgreSQL Experts Inc.
                                     http://www.pgexperts.com