| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Csaba Nagy <ncslists(at)googlemail(dot)com> |
| Cc: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, jd(at)commandprompt(dot)com, Thom Brown <thom(at)linux(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Andrew Dunstan <andrew(at)dunslane(dot)net>, Dave Page <dpage(at)pgadmin(dot)org>, Peter Eisentraut <peter_e(at)gmx(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Configuring synchronous replication |
| Date: | 2010-09-24 07:19:24 |
| Message-ID: | 1285312764.21874.1015.camel@ebony |
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| Lists: | pgsql-committers pgsql-hackers |
On Thu, 2010-09-23 at 14:26 +0200, Csaba Nagy wrote:
> Unfortunately it was quite long time ago we last tried, and I don't
> remember exactly what was bottlenecked. Our application is quite
> write-intensive, the ratio of writes to reads which actually reaches
> the disk is about 50-200% (according to the disk stats - yes,
> sometimes we write more to the disk than we read, probably due to the
> relatively large RAM installed). If I remember correctly, the standby
> was about the same regarding IO/CPU power as the master, but it was
> not able to process the WAL files as fast as they were coming in,
> which excludes at least the network as a bottleneck. What I actually
> suppose happens is that the one single process applying the WAL on the
> slave is not able to match the full IO the master is able to do with
> all it's processors.
>
> If you're interested, I could try to set up another try, but it would
> be on 8.3.7 (that's what we still run). On 9.x would be also
> interesting...
Substantial performance improvements came in 8.4 with bgwriter running
in recovery. That meant that the startup process didn't need to spend
time doing restartpoints and could apply changes continuously.
--
Simon Riggs www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Training and Services
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