Message-ID: <4C5744F5.3020805@agliodbs.com>
Date: Mon, 02 Aug 2010 15:21:41 -0700
From: Josh Berkus <josh@agliodbs.com>
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To: pgsql-performance@postgresql.org
Subject: Re: Testing Sandforce SSD
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> Definately - that 10% number was on the old-first hardware (the core 2
> E6600). After reading my post and the 185MBps with 18500 reads/s number
> I was a bit suspicious whether I did the tests on the new hardware with
> 4K, because 185MBps / 18500 reads/s is ~10KB / read, so I thought thats
> a lot closer to 8KB than 4KB. I checked with show block_size and it was
> 4K. Then I redid the tests on the new server with the default 8KB
> blocksize and got about 4700 tps (TPC-B/300)... 67/47 = 1.47. So it
> seems that on newer hardware, the difference is larger than 10%.

That doesn't make much sense unless there's some special advantage to a
4K blocksize with the hardware itself.  Can you just do a basic
filesystem test (like Bonnie++) with a 4K vs. 8K blocksize?

Also, are you running your pgbench tests more than once, just to account
for randomizing?

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