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Re: [PATCHES] Load distributed checkpoint patch

From: "Takayuki Tsunakawa" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>
To: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>, "Bruce Momjian" <bruce(at)momjian(dot)us>, "ITAGAKI Takahiro" <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp>, <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [PATCHES] Load distributed checkpoint patch
Date: 2006-12-22 03:26:22
Message-ID: 01a201c72578$f43b51e0$19527c0a@OPERAO (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
Hello, Mr. Grittner,

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
> We have 3,000 "directly connected" users, various business partner
> interfaces, and public web entry doing OLTP in 72 databases
distributed
> around the state, with real-time replication to central databases
which
> are considered derived copies.

What a big system you have.

>   If all the pages modified on the central
> databases were held in buffers or cache until after peak hours,
query
> performance would suffer -- assuming it would all even fit in cache.
We
> must have a way for dirty pages to be written under load while
> responding to hundreds of thousands of queries per hour without
> disturbing "freezes" during checkpoints.

I agree with you.  My words were not good.  I consider it is necessary
to always advance checkpoints even under heavy load, caring OLTP
transactions.

> I raise this only to be sure that such environments are considered
with
> these changes, not to discourage improvements in the checkpoint
> techniques.  We have effectively eliminated checkpoint problems in
our
> environment with a combination of battery backed controller cache
and
> aggressive background writer configuration.  When you have a patch
which
> seems to help those who still have problems, I'll try to get time
> approved to run a transaction replication stream onto one of our
servers
> (in "catch up mode") while we do a web "stress test" by playing back
> requests from our production log.  That should indicate how the
patch
> will affect us.

Thank you very much for your kind offer.



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