From owner-freebsd-current@FreeBSD.ORG Mon Mar 31 20:19:06 2008 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 92CEA106564A for ; Mon, 31 Mar 2008 20:19:06 +0000 (UTC) (envelope-from ivoras@gmail.com) Received: from el-out-1112.google.com (el-out-1112.google.com [209.85.162.176]) by mx1.freebsd.org (Postfix) with ESMTP id 3B57A8FC15 for ; Mon, 31 Mar 2008 20:19:06 +0000 (UTC) (envelope-from ivoras@gmail.com) Received: by el-out-1112.google.com with SMTP id v27so560563ele.12 for ; Mon, 31 Mar 2008 13:19:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=beta; h=domainkey-signature:received:received:message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references:x-google-sender-auth; bh=VxhPe/CLnGFg9j0bgC1gqtK5Z807Qe1BFdYgbKGrsVk=; b=ftTi22YV7p9n+I9xeea7buk9F11g6rdyzQ4FJ80cSkRJIeUrLWntH7MMrm0SqfJaGEj2WorEjZNu/cU6NmEupNiUYKO0eztCTjR7jKXmytH/agpro8HMer/JmakoaBiallu6c+nxKi9FmMslbKNNknJT5qpCn4M8OwAyJ+vLvRk= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=beta; h=message-id:date:from:sender:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references:x-google-sender-auth; b=VjzZE8Bns1Z6JxsFkuRom7KB0zWWcv/Q76G3+mzf/fczb9inL4nWBcIIpPo6jZdtXjg/spfZypqcAITB+mLsYn0h6UT74mbGxGmk2mjfzprzZI+6r5pTfcIjUfhz+9qFcJVRlX77aQVNroW7/EQyvuXlvfKtaYKi2AnXKyl8qz0= Received: by 10.141.20.7 with SMTP id x7mr3679282rvi.255.1206993080479; Mon, 31 Mar 2008 12:51:20 -0700 (PDT) Received: by 10.141.212.1 with HTTP; Mon, 31 Mar 2008 12:51:20 -0700 (PDT) Message-ID: <9bbcef730803311251l79af84b1j7a3a8018442a6478@mail.gmail.com> Date: Mon, 31 Mar 2008 21:51:20 +0200 From: "Ivan Voras" Sender: ivoras@gmail.com To: d@delphij.net In-Reply-To: <47F133AE.2010900@delphij.net> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <47F133AE.2010900@delphij.net> X-Google-Sender-Auth: 9b28a4ae39efbfcc Cc: freebsd-current@freebsd.org Subject: Re: Are large RAID stripe sizes useful with FreeBSD? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 31 Mar 2008 20:19:06 -0000 On 31/03/2008, Xin LI wrote: > Ivan Voras wrote: > > Most of new hardware RAID controllers offer stripe sizes of 128K, 256K > > and some also have 512K and 1M stripes. In the simplest case of RAID0 of > > two drives, knowing that the data is striped across the drives and that > > FreeBSD issues IO request of at most 64K, is it useful to set stripe > > sizes to anything larger than 32K? I suppose something like TCQ would > > help the situation but does anyone know how is this situation usually > > handled on the RAID controllers? > > Short answer: yes. Larger stripe sizes would allow better performance > for continuous read/write. In theory they will negatively affect small > size read/write but in practice you will notice that larger stripe size > would give better performance in almost all cases. Ok, I'm interested in how it works. Are the IO requests queued at the controller until there's enough of them to write a stripe block?