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Date:      Sun, 18 Feb 2007 00:38:14 +0100
From:      Ivan Voras <ivoras@fer.hr>
To:        freebsd-questions@freebsd.org
Subject:   Re: A bottleneck in gstripe?
Message-ID:  <er83lg$9l2$1@sea.gmane.org>
In-Reply-To: <200702171434.15077.kirk@strauser.com>
References:  <200702171434.15077.kirk@strauser.com>

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Kirk Strauser wrote:
> I built a gstripe volume with 4 drives and a 128KB stripesize.  When ru=
nning=20
> one particular application, gstat reports that stripe/stripe1 is 99% bu=
sy,=20
> although its four drives are running at less than 30% each.  Am I=20
> misinterpreting the numbers - maybe the total is the sum of the drives?=
 -=20
> or is there some giant overhead that I'm missing?

Nevermind the "% used" number, it's an approximation of an approximation
- how is your real world performance? For example, use
ports/benchmarks/bonnie++ .

> I've set kern.geom.stripe.fast=3D1, and kern.geom.stripe.fast_failed st=
ays at=20
> 0.  I don't have enough experience with geom_strip to even know where t=
o go=20
> from here.  Are stripe sizes likely to make much of a difference when t=
he=20
> heaviest load is when PostgreSQL is receiving massive imports?  This is=
 a=20

Not much, as the data is first written to WAL, which goes at full file
system speed (no fsyncs).



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