| From: | Greg Smith <greg(at)2ndQuadrant(dot)com> |
|---|---|
| To: | pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: VX_CONCURRENT flag on vxfs( 5.1 or later) for performance for postgresql? |
| Date: | 2011-04-29 00:14:16 |
| Message-ID: | 4DBA02D8.4050705@2ndQuadrant.com |
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| Lists: | pgsql-hackers pgsql-novice pgsql-performance |
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(at)2ndQuadrant(dot)com Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.us
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