Date: Sat, 30 Sep 2000 21:09:45 -0700 From: Mike Smith <msmith@freebsd.org> To: karsten@rohrbach.de Cc: Greg Lehey <grog@lemis.com>, Esko Petteri Matinsola <esko@kapi.net>, Clark Shishido <clark@desktop.com>, hackers@FreeBSD.ORG Subject: Re: Vinum RAID-5 performance problem Message-ID: <200010010409.e9149jh01025@mass.osd.bsdi.com> In-Reply-To: Your message of "Sun, 01 Oct 2000 05:52:36 %2B0200." <20001001055235.G83678@rohrbach.de>
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> Greg Lehey(grog@lemis.com)@Sat, Sep 09, 2000 at 11:33:19AM +0930:
> [...]
> > depends on what you're trying to do. But yes, having only two
> > controllers will halve your RAID-5 write performance. Note also that
> > with a 256 kB stripe, you'll run into drive contention problems
> > because all your superblocks will be on the same subdisk. Take a size
> > like 273 kB, for example.
> or (now proven fact) grog's first guess to solve my config problems:
> 511k ;-) which ran like a charm on dang big box (32x18.3gig)
> greg, you should underline that fact in your docs at a prominent
> location. i think that using a plex size which is even or too small are
> the most common configuration mistakes the people do...
I should point out (and undermine my position 8) that this is one of the
*major* performance advantages that Vinum has over most, if not all
hardware RAID controllers - oddball stripe sizes interact much better
with FFS than the small-power-of-2 that you're stuck with on a hardware
RAID controller.
--
... every activity meets with opposition, everyone who acts has his
rivals and unfortunately opponents also. But not because people want
to be opponents, rather because the tasks and relationships force
people to take different points of view. [Dr. Fritz Todt]
V I C T O R Y N O T V E N G E A N C E
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