From owner-freebsd-stable@FreeBSD.ORG Sat Aug 14 00:36:38 2010 Return-Path: Delivered-To: stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id BA41B1065670 for ; Sat, 14 Aug 2010 00:36:38 +0000 (UTC) (envelope-from rsmith@xs4all.nl) Received: from smtp-vbr14.xs4all.nl (smtp-vbr14.xs4all.nl [194.109.24.34]) by mx1.freebsd.org (Postfix) with ESMTP id 34D178FC17 for ; Sat, 14 Aug 2010 00:36:37 +0000 (UTC) Received: from slackbox.erewhon.net (slackbox.xs4all.nl [213.84.242.160]) by smtp-vbr14.xs4all.nl (8.13.8/8.13.8) with ESMTP id o7E0aWVE074179; Sat, 14 Aug 2010 02:36:32 +0200 (CEST) (envelope-from rsmith@xs4all.nl) Received: by slackbox.erewhon.net (Postfix, from userid 1001) id 2E59CBAAD; Sat, 14 Aug 2010 02:36:32 +0200 (CEST) Date: Sat, 14 Aug 2010 02:36:31 +0200 From: Roland Smith To: Clifton Royston Message-ID: <20100814003631.GA34499@slackbox.erewhon.net> References: <20100813160109.8BDDA1CC3A@ptavv.es.net> <20100813213205.GB29150@slackbox.erewhon.net> <20100813233612.GB4280@lava.net> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="GvXjxJ+pjyke8COw" Content-Disposition: inline In-Reply-To: <20100813233612.GB4280@lava.net> X-GPG-Fingerprint: 1A2B 477F 9970 BA3C 2914 B7CE 1277 EFB0 C321 A725 X-GPG-Key: http://www.xs4all.nl/~rsmith/pubkey.txt X-GPG-Notice: If this message is not signed, don't assume I sent it! User-Agent: Mutt/1.5.20 (2009-06-14) X-Virus-Scanned: by XS4ALL Virus Scanner Cc: stable@freebsd.org Subject: Re: Inconsistent IO performance X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 14 Aug 2010 00:36:38 -0000 --GvXjxJ+pjyke8COw Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Aug 13, 2010 at 01:36:12PM -1000, Clifton Royston wrote: > > Both figures seem quite low to me? I cannot exactly reproduce your test, > > because I don't have an empty second disk handy, but doing > >=20 > > dd if=3D/dev/zero bs=3D1m count=3D100 of=3D/tmp/foo > =20 > With a total write size of 100MB, aren't you just testing speed of > writing into cache RAM this way? I think you need to write amounts > dramatically greater than the total size of the RAM to get values which > appropriately measure disk speed. > This also supports that theory - off the top of my head, maximum > theoretical possible write throughput to a similarly sized 7200rpm > drive should be 70MB/s (buffer to disk data transfer rate according to > WDC's specs.) Ok, so I tried this; dd if=3D/dev/zero of=3D/tmp/foo bs=3D10M count=3D1000 10485760000 bytes transferred in 138.304953 secs (75816229 bytes/sec) 10485760000 bytes transferred in 139.125501 secs (75369073 bytes/sec) 10485760000 bytes transferred in 136.149871 secs (77016305 bytes/sec) Which is around 72 MiB/s with filesystem overhead, which sounds about right. The drive was making plenty of noise. The point is that it is _way_ more than the 18-22 MiB/s on a raw disk that Kevin is getting. I'll try the same on my laptop topmorrow and see what that gets me. This de= sktop machine is ICH7 with ata(4), laptop is ICH9 with ahci(4). Roland --=20 R.F.Smith http://www.xs4all.nl/~rsmith/ [plain text _non-HTML_ PGP/GnuPG encrypted/signed email much appreciated] pgp: 1A2B 477F 9970 BA3C 2914 B7CE 1277 EFB0 C321 A725 (KeyID: C321A725) --GvXjxJ+pjyke8COw Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.16 (FreeBSD) iEYEARECAAYFAkxl5Q8ACgkQEnfvsMMhpyUPqQCfZRNSTI7QOlTZcT2tRiX6HLEv WjoAoIzAO725qD+qYyw+7yaR+ztRs7gl =Tks/ -----END PGP SIGNATURE----- --GvXjxJ+pjyke8COw--