From owner-svn-src-head@FreeBSD.ORG Wed Jan 6 19:03:45 2010 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id A5B0D106568B; Wed, 6 Jan 2010 19:03:45 +0000 (UTC) (envelope-from ivoras@gmail.com) Received: from ey-out-2122.google.com (ey-out-2122.google.com [74.125.78.24]) by mx1.freebsd.org (Postfix) with ESMTP id B912A8FC15; Wed, 6 Jan 2010 19:03:44 +0000 (UTC) Received: by ey-out-2122.google.com with SMTP id 22so881196eye.9 for ; Wed, 06 Jan 2010 11:03:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:sender:received:in-reply-to :references:from:date:x-google-sender-auth:message-id:subject:to:cc :content-type; bh=soXwXsriCnPocEk3BSBLKLTePyGHCTAbH4C2g2zOhxM=; b=Iwjib4TdmDgVMXHpfqYU0GxPRMu1tFMhf9gIZMRvyh4p5cS7DNAcxeeyn1tNR7i+Ip qIx/2hQ2/hqAlayMGecMTcnzTI0Kz8OLxPXwDbJObxjL/H/fxidPkU64OF3cZL8IH17v pCG/gnLvokuVd02PIPzKrV+GqsqLGge6RRZnM= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:from:date :x-google-sender-auth:message-id:subject:to:cc:content-type; b=wK7G9CEb2w+aSzPnlYHZV3/mnt7KoReiV6g+0qG8tyBNRFAgwweSWCh3vaKlksvk/5 9CPYl+0c/2AAiT/s+AhsSvQbSybiORZnnUrvWjt3KMLdG1UfHsTL84yRjh4z//xl7cAx 4SdOpG3c8vU8a+i/cJgXsIn7vOa329mBgzzes= MIME-Version: 1.0 Sender: ivoras@gmail.com Received: by 10.216.86.85 with SMTP id v63mr470777wee.32.1262804617027; Wed, 06 Jan 2010 11:03:37 -0800 (PST) In-Reply-To: <4B44D8FA.2000608@FreeBSD.org> References: <201001061712.o06HCICF087127@svn.freebsd.org> <9bbcef731001060938k2b0014a2m15eef911b9922b2c@mail.gmail.com> <4B44D8FA.2000608@FreeBSD.org> From: Ivan Voras Date: Wed, 6 Jan 2010 20:03:16 +0100 X-Google-Sender-Auth: 2db26b6cfc458966 Message-ID: <9bbcef731001061103u33fd289q727179454b21ce18@mail.gmail.com> To: Alexander Motin Content-Type: text/plain; charset=UTF-8 Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r201658 - head/sbin/geom/class/stripe X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 06 Jan 2010 19:03:45 -0000 2010/1/6 Alexander Motin : > Ivan Voras wrote: >> I think there was one more reason - though I'm not sure if it is still >> valid because of your current and future work - the MAXPHYS >> limitation. If MAXPHYS is 128k, with 64k stripes data was only to be >> read from maximum of 2 drives. With 4k stripes it would have been read >> from 128/4=32 drives, though I agree 4k is too low in any case >> nowadays. I usually choose 16k or 32k for my setups. > > While you are right about MAXPHYS influence, and I hope we can rise it > not so far, IMHO it is file system business to manage deep enough > read-ahead/write-back to make all drives busy, independently from > MAXPHYS value. With small MAXPHYS value FS should just generate more > requests in advance. Except some RAID3/5/6 cases, where short writes > ineffective, MAXPHYS value should only affect processing overhead. Yes, my experience which lead to the post was mostly on UFS which, while AFAIK it does read-ahead, it still does it serially (I think this is implied by your experiments with NCQ and ZFS vs UFS) - so in any case only 2 drives are hit with 64k stripe size at any moment in time. In any case, as you say it is tunable so personal preferences can be applied. Thanks!