From owner-freebsd-hackers@FreeBSD.ORG Fri Jan 18 18:19:03 2013 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id D20A88A8 for ; Fri, 18 Jan 2013 18:19:03 +0000 (UTC) (envelope-from scott4long@yahoo.com) Received: from nm23-vm2.bullet.mail.ne1.yahoo.com (nm23-vm2.bullet.mail.ne1.yahoo.com [98.138.91.211]) by mx1.freebsd.org (Postfix) with ESMTP id 9AEFCDED for ; Fri, 18 Jan 2013 18:19:03 +0000 (UTC) Received: from [98.138.226.180] by nm23.bullet.mail.ne1.yahoo.com with NNFMP; 18 Jan 2013 18:18:57 -0000 Received: from [98.138.89.251] by tm15.bullet.mail.ne1.yahoo.com with NNFMP; 18 Jan 2013 18:18:56 -0000 Received: from [127.0.0.1] by omp1043.mail.ne1.yahoo.com with NNFMP; 18 Jan 2013 18:18:56 -0000 X-Yahoo-Newman-Property: ymail-3 X-Yahoo-Newman-Id: 980127.71061.bm@omp1043.mail.ne1.yahoo.com Received: (qmail 75771 invoked by uid 60001); 18 Jan 2013 18:18:56 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yahoo.com; s=s1024; t=1358533136; bh=hHB3LbEoQLKpgIsN5zv351jdCwlj/MhT6GgHn/7HQRI=; h=X-YMail-OSG:Received:X-Rocket-MIMEInfo:X-Mailer:References:Message-ID:Date:From:Reply-To:Subject:To:Cc:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding; b=ClJUSKncYi2wawBSsNMNMY4zvSFkfByOBGGxuF8WcIro8L2K7jS1Z3fHOk4TwrnQzcQ0c6zU1Chr3EG1SPpCERgPJrZwHlw7NSR6sCreH5iQ5On23o14wlKFfRC9bmXL8jEU6SHRqqypyTf/o+4y9UpHOQdfTmh7vJBI4dq6/Cw= DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com; h=X-YMail-OSG:Received:X-Rocket-MIMEInfo:X-Mailer:References:Message-ID:Date:From:Reply-To:Subject:To:Cc:In-Reply-To:MIME-Version:Content-Type:Content-Transfer-Encoding; b=vGOnJ5ic92XbLLxWc9pxk3fxQWWWPlXvEq6XsUNf+UwpaYDTFZvHSB1WRZv9JzlyrXRkYfkX67LCPMJHSaS2gEx33JrLKitmi4LWioThkzBKUiC/ATVopKDdsVaG66hauAa0Yvd5YpiN88zra1a+JVeURgaWKE0342w+FbbZ7Ko=; X-YMail-OSG: iftSZWYVM1kvTKgTBmAjEni.Y4uiZ_8_3ksNFa2g.qsG4w2 UHnLAvaj9kjK2IkaU8OTNcNP8OdiRrN39VniyrvpHj2qrTtfi4y4fJndPkIJ x_vZZd6FG9sJp.423vJ_oX7xJTkkjb63aJ1XDc6fPMR29S9Z3HI7P.ZSnTHh 6xKEZdaqwx7Jkn9KMUYgX7IgqbGPJ7jIQjHapo7pnQycqBpFzF2nZMROiEn3 Zqr27BibI6xi7nCKUxNIQy17n_bXsuNWGSOgxmTby.bjnF5.MnLxwscZKEN3 OGhCibxA5cP9ZZoRNI0r1FcmCSz86kqwSQq1bWkr9UYrr0dTdzrtxW4Fd7eR lORrHqGXtRSZHlmFk7c4CxoqIKzJkI7fq2LrDaPuij47tF7g.nGnudHsEJD0 T6.2X46Vefvv6nvkfzFpgaCScDNCkA0xmwRDdpsGZKETOBmS_oE1deOkugpW bJjchqgHPX7NwvOlHbBAzIfeTEBOSMfiL.1CQY0SF8QR49CupVHQKLj.fCG3 hb5IizpIYCm6nfUx1ArUOtSB0 Received: from [69.53.237.126] by web120302.mail.ne1.yahoo.com via HTTP; Fri, 18 Jan 2013 10:18:56 PST X-Rocket-MIMEInfo: 001.001, LS0tLS0gT3JpZ2luYWwgTWVzc2FnZSAtLS0tLQoKPiBGcm9tOiBXb2pjaWVjaCBQdWNoYXIgPHdvanRla0B3b2p0ZWsudGVuc29yLmdkeW5pYS5wbD4KPiBUbzogU2NvdHQgTG9uZyA8c2NvdHQ0bG9uZ0B5YWhvby5jb20.Cj4gQ2M6IERpZXRlciBCU0QgPGRpZXRlcmJzZEBnbWFpbC5jb20.OyAiZnJlZWJzZC1oYWNrZXJzQGZyZWVic2Qub3JnIiA8ZnJlZWJzZC1oYWNrZXJzQGZyZWVic2Qub3JnPjsgImdpYmJzQEZyZWVCU0Qub3JnIiA8Z2liYnNAZnJlZWJzZC5vcmc.OyAic2NvdHRsQEZyZWVCU0Qub3JnIiABMAEBAQE- X-Mailer: YahooMailWebService/0.8.130.494 References: <1358529778.71931.YahooMailNeo@web120304.mail.ne1.yahoo.com> Message-ID: <1358533136.41693.YahooMailNeo@web120302.mail.ne1.yahoo.com> Date: Fri, 18 Jan 2013 10:18:56 -0800 (PST) From: Scott Long Subject: Re: IBM blade server abysmal disk write performances To: Wojciech Puchar In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable X-Mailman-Approved-At: Fri, 18 Jan 2013 18:30:48 +0000 Cc: "freebsd-hackers@freebsd.org" , Dieter BSD , "gibbs@FreeBSD.org" , "scottl@FreeBSD.org" , "mjacob@FreeBSD.org" X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list Reply-To: Scott Long List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 18 Jan 2013 18:19:03 -0000 ----- Original Message -----=0A=0A> From: Wojciech Puchar =0A> To: Scott Long =0A> Cc: Dieter BS= D ; "freebsd-hackers@freebsd.org" ; "gibbs@FreeBSD.org" ; "scottl@FreeBSD.org" ; "mjacob@FreeBSD.org" =0A> Sent: Fri= day, January 18, 2013 11:10 AM=0A> Subject: Re: IBM blade server abysmal di= sk write performances=0A> =0A>> =0A>> The default value, -1, instructs the= driver to leave the STA drives at =0A> their configuration default. =A0Oft= en times this means that the MPT BIOS will turn =0A> off the write cache on= every system boot sequence. =A0IT DOES THIS FOR A GOOD =0A> REASON! =A0An = enabled write cache is counter to data reliability. =A0Yes, it helps =0A> m= ake benchmarks look really good, and it's acceptable if your data can be = =0A> safely thrown away (for example, you're just caching from a slower sou= rce, =0A> and the cache can be rebuilt if it gets corrupted). =A0And yes, L= inux has many =0A> tricks to make this benchmark look really good. =A0The t= ricks range from buffering =0A> the raw device to having 'dd' recognize the= requested task and =0A> short-circuit the process of going to /dev/null or= pulling from /dev/zero. =A0I =0A> can't tell you how bogus these tests are= and how completely irrelevant they =0A> are in predicting actual workload = performance. =A0But, I'm not going to stop =0A> anyone from trying, so give= the above tunable a try=0A>> and let me know how it works.=0A>> =0A> If c= omputer have UPS then write caching is fine. even if FreeBSD crash, =0A> di= sk would write data=0A> =0A=0AI suspect that I'm encountering situations ri= ght now at netflix where this advice is not true. =A0I have drives that are= seeing intermittent errors, then being forced into reset after a timeout, = and then coming back up with filesystem problems. =A0It's only a suspicion = at this point, not a confirmed case.=0A=0AScott=0A