Re: 8.3 synchronous_commit - Mailing list pgsql-performance

From Hannes Dorbath
Subject Re: 8.3 synchronous_commit
Date
Msg-id 4795DA0B.7000202@theendofthetunnel.de
Whole thread Raw
In response to Re: 8.3 synchronous_commit  ("Guillaume Smet" <guillaume.smet@gmail.com>)
List pgsql-performance
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

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