From: Greg Smith <greg@2ndQuadrant.com>
To: pgsql-performance@postgresql.org
Subject: Re: VX_CONCURRENT flag on vxfs( 5.1 or later) for performance for postgresql?
Date: Thu, 28 Apr 2011 20:14:16 -0400
Message-ID: <4DBA02D8.4050705@2ndQuadrant.com> (raw)
In-Reply-To: <BANLkTinBLhq8mYyeVupWz5J02OWfbTK_nA@mail.gmail.com>
References: <BANLkTinBLhq8mYyeVupWz5J02OWfbTK_nA@mail.gmail.com>
On 04/27/2011 11:33 PM, HSIEN-WEN CHU wrote:
> When database files are on a VxFS filesystem, performance can be
> significantly improved by setting the VX_CONCURRENT cache advisory on
> the file according to vxfs document,
>
That won't improve performance, and it's not safe either. VX_CONCURRENT
switches the filesystem to use direct I/O. That's usually slower for
PostgreSQL. And it introduces some requirements for both block
alignment and the application avoiding overlapping writes. PostgreSQL
doesn't do either, so I wouldn't expect it to be compatible with
VX_CONCURRENT.
--
Greg Smith 2ndQuadrant US greg@2ndQuadrant.com Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.us
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To: pgsql-performance@postgresql.org
Cc: greg@2ndQuadrant.com
Subject: Re: VX_CONCURRENT flag on vxfs( 5.1 or later) for performance for postgresql?
In-Reply-To: <4DBA02D8.4050705@2ndQuadrant.com>
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