Date: Tue, 9 Jan 2007 11:11:45 +0100 From: Pawel Jakub Dawidek <pjd@FreeBSD.org> To: Ahnjoan Amous <ahnjoan@gmail.com> Cc: freebsd-geom@freebsd.org Subject: Re: GEOM mirror performance - slow Message-ID: <20070109101144.GB62430@garage.freebsd.pl> In-Reply-To: <5e575c8a0701081957k43483e1ewf9b27022ae330d8a@mail.gmail.com> References: <5e575c8a0701081957k43483e1ewf9b27022ae330d8a@mail.gmail.com>
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On Mon, Jan 08, 2007 at 10:57:14PM -0500, Ahnjoan Amous wrote:
> I'm sorry about the double posting, I have switch e-mail clients and
> hope that the text is now understandable.
>=20
> While deploying 6.1-RELEASE I'm seeing slower than expected speed
> using geom mirror.
[...]
Hard to say, really. It depends on many factors. On my test system:
# dd if=3D/dev/zero of=3D/dev/ad4d bs=3D1m count=3D1000 &; dd if=3D/dev/ze=
ro of=3D/dev/ad6d bs=3D1m count=3D1000
ad4d: 64.27MB/s
ad6d: 61.49MB/s
# gmirror label foo ad4d ad6d
# dd if=3D/dev/zero of=3D/dev/mirror/foo bs=3D1m count=3D1000
mirror/foo: 61.26MB/s
BUT disks can somehow interfere with each other (are on the same ATA
channel, etc.).
On this system I've this setup:
ATA channel 2:
Master: ad4 <ST3808110AS/3.AAD> Serial ATA II
Slave: ad5 <ST3808110AS/3.AAD> Serial ATA II
ATA channel 3:
Master: ad6 <ST3808110AS/3.AAD> Serial ATA II
Slave: no device present
As you saw above, I was using ad4 and ad6, which are on different ATA
channels. When I do the same experiment for ad4 and ad5 I see worser
results:
# dd if=3D/dev/zero of=3D/dev/ad4d bs=3D1m count=3D1000 &; dd if=3D/dev/ze=
ro of=3D/dev/ad5d bs=3D1m count=3D1000
ad4d: 59.55MB/s
ad5d: 59.31MB/s
# gmirror label foo ad4d ad5d
# dd if=3D/dev/zero of=3D/dev/mirror/foo bs=3D1m count=3D1000
mirror/foo: 49.03MB/s
So not ~40% slowdown as in your case, but still visible slowdown (~20%).
--=20
Pawel Jakub Dawidek http://www.wheel.pl
pjd@FreeBSD.org http://www.FreeBSD.org
FreeBSD committer Am I Evil? Yes, I Am!
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