Re: Spread checkpoint sync

From: Cédric Villemain <cedric(dot)villemain(dot)debian(at)gmail(dot)com>
To: Greg Smith <greg(at)2ndquadrant(dot)com>
Cc: Bruce Momjian <bruce(at)momjian(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Spread checkpoint sync
Date: 2011-01-18 10:26:51
Message-ID: AANLkTimtkCUi0S9to_PHaGSztHeeBY3gxt2DZr3AhJBX@mail.gmail.com
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2011/1/18 Greg Smith <greg(at)2ndquadrant(dot)com>:
> Bruce Momjian wrote:
>>
>> Should we be writing until 2:30 then sleep 30 seconds and fsync at 3:00?
>>
>
> The idea of having a dead period doing no work at all between write phase
> and sync phase may have some merit.  I don't have enough test data yet on
> some more fundamental issues in this area to comment on whether that smaller
> optimization would be valuable.  It may be a worthwhile concept to throw
> into the sequencing.

Are we able to have some pause without strict rules like 'stop for 30
sec' ? (case : my hardware is very good and I can write 400MB/sec with
no interrupt, XXX IOPS)

I wonder if we are not going to have issue with "RAID firmware + BBU
+ linux scheduler" because we are adding 'unexpected' behavior in the
middle.

--
Cédric Villemain               2ndQuadrant
http://2ndQuadrant.fr/     PostgreSQL : Expertise, Formation et Support

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