From owner-freebsd-hackers@FreeBSD.ORG Fri Jan 18 06:54:09 2013 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115]) by hub.freebsd.org (Postfix) with ESMTP id B1F96E6B; Fri, 18 Jan 2013 06:54:09 +0000 (UTC) (envelope-from mj@feral.com) Received: from ns1.feral.com (ns1.feral.com [192.67.166.1]) by mx1.freebsd.org (Postfix) with ESMTP id 6855CB6; Fri, 18 Jan 2013 06:54:08 +0000 (UTC) Received: from [192.168.1.227] (108-85-197-34.lightspeed.irvnca.sbcglobal.net [108.85.197.34]) (authenticated bits=0) by ns1.feral.com (8.14.5/8.14.4) with ESMTP id r0I6q7YD034092 (version=TLSv1/SSLv3 cipher=DHE-RSA-CAMELLIA256-SHA bits=256 verify=NO); Thu, 17 Jan 2013 22:52:08 -0800 (PST) (envelope-from mj@feral.com) Message-ID: <50F8F111.3060907@feral.com> Date: Thu, 17 Jan 2013 22:52:01 -0800 From: Matthew Jacob Organization: Feral Software User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130107 Thunderbird/17.0.2 MIME-Version: 1.0 To: Dieter BSD Subject: Re: IBM blade server abysmal disk write performances References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.7 (ns1.feral.com [192.67.166.1]); Thu, 17 Jan 2013 22:52:08 -0800 (PST) Cc: freebsd-hackers@freebsd.org, 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: mj@feral.com 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 06:54:09 -0000 On 1/17/2013 8:03 PM, Dieter BSD wrote: > I think it is time to ask the driver wizards why TCQ isn't working, so > I'm cc-ing the authors listed on the mpt man page. It is the MPT firmware that implements SATL, but there are probably tweaks that the FreeBSD driver doesn't do that the Linux driver does do. The MPT driver was also worked on years ago and for a variety of reasons is unloved. In general ATA drives have caching enabled, and in fact it is difficult to turn off. There is no info in the email trail that says what the state of the SAS drive is wrt cache enable. There is also no information in the original email as to which direction the I/O was being sent. Let's also get a grip about linux vs. freebsd- using 'dd' is not necessarily and apple-apple comparison where writes are concerned because of the linux heavy write behind policy (plugging I/Os until it gets a large xfer built up and then releasing, which gets larger xfers, while freebsd will use the blocksize you tell it to (whether that's optimal or not). I'll see if I can generate some A/B numbers using fio here and report back.