From owner-freebsd-hackers@freebsd.org Mon Oct 10 12:14:40 2016 Return-Path: Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id C1793C07538 for ; Mon, 10 Oct 2016 12:14:40 +0000 (UTC) (envelope-from nkoch@demig.de) Received: from demig.de (demig.de [81.169.228.196]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "Parallels Panel", Issuer "Parallels Panel" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 1A451B6B for ; Mon, 10 Oct 2016 12:14:39 +0000 (UTC) (envelope-from nkoch@demig.de) Received: (qmail 30321 invoked from network); 10 Oct 2016 14:06:55 +0200 Received: from b2b-130-180-89-86.unitymedia.biz (HELO firewall.demig.intra) (130.180.89.86) by demig.de with ESMTPSA (DHE-RSA-AES256-SHA encrypted, authenticated); 10 Oct 2016 14:06:55 +0200 Received: from SRV-FS-2.Demig.intra (nameserver.demig.intra [192.168.148.248]) by firewall.demig.intra (8.14.4/8.14.4) with ESMTP id u9AC6lAR073358 for ; Mon, 10 Oct 2016 14:06:47 +0200 (CEST) (envelope-from nkoch@demig.de) Received: from [192.168.148.215] (192.168.148.215) by SRV-FS-2 (192.168.148.248) with Microsoft SMTP Server (TLS) id 14.3.123.3; Mon, 10 Oct 2016 14:06:41 +0200 From: Norbert Koch Subject: Why at least 4 cylinder groups? To: References: <56A9D502.7010809@demig.de> <1453995911.1275.14.camel@freebsd.org> <56AA42CF.10408@demig.de> <1454001217.1275.19.camel@freebsd.org> Message-ID: Date: Mon, 10 Oct 2016 14:06:41 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.3.0 MIME-Version: 1.0 In-Reply-To: <1454001217.1275.19.camel@freebsd.org> Content-Type: text/plain; charset="windows-1252"; format=flowed Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.73 on 192.168.148.235 X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 10 Oct 2016 12:14:40 -0000 Hello. In an embedded system I am having a rather small (static) ram disk of about 1.5MB, formatted as UFS(1). Under FreeBSD 4 dumpfs shows me there is 1 cylinder group. Under FreeBSD 9 and 10 I see 4 cylinder groups. 4 is hard coded as the minimum value in ufs/ffs/fs.h. Why? Is there any technical reason not to have less than 4 cylinder groups? For my application the wasted 188KB make a difference. Thank you, Norbert Koch