From: Hannes Dorbath <light@theendofthetunnel.de>
Subject: Re: 8.3 synchronous_commit
Date: Tue, 22 Jan 2008 12:56:59 +0100
Organization: Hub.Org Networking Services
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Message-ID: <4795DA0B.7000202@theendofthetunnel.de>
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	<1d4e0c10801220049p7b184a52s1b2b2e86bc414395@mail.gmail.com>
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To: Guillaume Smet <guillaume.smet@gmail.com>
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To: pgsql-performance@postgresql.org

Guillaume Smet wrote:
> Also with SATA? If your SATA disk is lying about effectively SYNCing
> the data, I'm not that surprised you don't see any improvement. Being
> slower is a bit surprising though.

The disc is not lying, but LVM does not support write barriers, so the 
result is the same. Indeed nothing is flushing the disc's write cache on 
fsync. However I could disable the disc's write cache entirely. One 
reason why I'm a ZFS fan boy lately. It just get's all of this right by 
*default*.

Anyway, with some further testing my benchmark results vary so much that 
  further discussion seems pointless. I'll repost when I really have 
reproducible values and followed Greg Smith's advice.


-- 
Best regards,
Hannes Dorbath