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* PITR load on servers - increased 20%
@ 2010-03-16 10:05 Renato Oliveira <renato.oliveira@grant.co.uk>
2010-03-17 13:55 ` Re: PITR load on servers - increased 20% Kevin Grittner <Kevin.Grittner@wicourts.gov>
2010-03-18 09:07 ` Re: PITR load on servers - increased 20% Simon Riggs <simon@2ndQuadrant.com>
0 siblings, 2 replies; 3+ messages in thread
From: Renato Oliveira @ 2010-03-16 10:05 UTC (permalink / raw)
To: pgsql-admin
Dear all,
I have been testing PITR and I have noticed a 20% increase on the load of the Disk subsystem.
Is that a normal thing to expect? Have you come across this or have you noticed this increase?
I know some of you guys have been using it for quite some time, would you mind in sharing your experiences, please?
Thank you very much
Best regards
Renato
Renato Oliveira
Systems Administrator
e-mail: renato.oliveira@grant.co.uk
Tel: +44 (0)1763 260811
Fax: +44 (0)1763 262410
http://www.grant.co.uk/
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^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: PITR load on servers - increased 20%
2010-03-16 10:05 PITR load on servers - increased 20% Renato Oliveira <renato.oliveira@grant.co.uk>
@ 2010-03-17 13:55 ` Kevin Grittner <Kevin.Grittner@wicourts.gov>
1 sibling, 0 replies; 3+ messages in thread
From: Kevin Grittner @ 2010-03-17 13:55 UTC (permalink / raw)
To: Renato Oliveira <renato.oliveira@grant.co.uk>; +Cc: pgsql-admin
Renato Oliveira <renato.oliveira@grant.co.uk> wrote:
> I have been testing PITR and I have noticed a 20% increase on the
> load of the Disk subsystem.
>
> Is that a normal thing to expect?
It depends on your workload and archive script, but that doesn't
seem too shocking.
For one thing, turning on archiving causes more to be written to the
WAL files, so you should expect some increase just by enabling
archiving, even if your archive script just consists of 'exit 0'.
Reading the WAL file in the archive script will often be reading
from OS cache, but not necessarily. If you're copying the WAL files
to a local file system (which often makes sense), that obviously
increases I/O. If there's enough delay between the archive script
writing the file to a local drive and something (e.g., rsync)
picking it up, it might need to read from the disk, and rsync is
likely to do some logging.
I would be surprised if you couldn't measure any increase, and 20%
is certainly within a reasonable range, depending on all the above.
If you need to try to minimize the impact, besides considering all
of the above, you might want to look at the full_page_writes
configuration option.
http://www.postgresql.org/docs/8.4/interactive/runtime-config-wal.html#GUC-FULL-PAGE-WRITES
-Kevin
^ permalink raw reply [nested|flat] 3+ messages in thread
* Re: PITR load on servers - increased 20%
2010-03-16 10:05 PITR load on servers - increased 20% Renato Oliveira <renato.oliveira@grant.co.uk>
@ 2010-03-18 09:07 ` Simon Riggs <simon@2ndQuadrant.com>
1 sibling, 0 replies; 3+ messages in thread
From: Simon Riggs @ 2010-03-18 09:07 UTC (permalink / raw)
To: Renato Oliveira <renato.oliveira@grant.co.uk>; +Cc: pgsql-admin
On Tue, 2010-03-16 at 10:05 +0000, Renato Oliveira wrote:
> I have been testing PITR and I have noticed a 20% increase on the load of the Disk subsystem.
>
> Is that a normal thing to expect? Have you come across this or have you noticed this increase?
>
> I know some of you guys have been using it for quite some time, would you mind in sharing your experiences, please?
I think you need to explain what things you've been testing and how.
There are some well documented bulk data load optimizations that we
cannot take advantage of when running archiving, but apart from those
the load is actually very low in normal running.
--
Simon Riggs www.2ndQuadrant.com
^ permalink raw reply [nested|flat] 3+ messages in thread
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2010-03-16 10:05 PITR load on servers - increased 20% Renato Oliveira <renato.oliveira@grant.co.uk>
2010-03-17 13:55 ` Kevin Grittner <Kevin.Grittner@wicourts.gov>
2010-03-18 09:07 ` Simon Riggs <simon@2ndQuadrant.com>
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