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Re: testing HS/SR - 1 vs 2 performance

From: "Erik Rijkers" <er(at)xs4all(dot)nl>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "Simon Riggs" <simon(at)2ndquadrant(dot)com>, "Robert Haas" <robertmhaas(at)gmail(dot)com>, "Heikki Linnakangas" <heikki(dot)linnakangas(at)enterprisedb(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: testing HS/SR - 1 vs 2 performance
Date: 2010-04-25 21:52:19
Message-ID: 32176e37d35c69ee4a2295a2a4b08812.squirrel@webmail.xs4all.nl (view raw or flat)
Thread:
Lists: pgsql-hackers
On Sun, April 25, 2010 20:55, Tom Lane wrote:
>
> That seems weird.  Why do most of the runs show primary and standby
> as having comparable speed, but a few show the standby as much slower?
> The parameters for those runs don't seem obviously different from cases
> where it's fast.  I think there might have been something else going on
> on the standby during those runs.  Or do you think those represent
> cases where the mystery slowdown event happened?
>

the strange case is the scale 100 standby's slow start, followed by
a steady increase during -c 1, then -c 10, and finally getting up to speed
with -c 20 (and up).  And these slow-but-growing standby series are interspersed
with normal (high-speed) primary series.

I'll try to repeat this pattern on other hardware; although
if my tests were run with faulty hardware I wouldn't know how/why
that would give the above effect (such a 'regular aberration').


testing is more difficult than I thought...


Erik Rijkers


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