From owner-freebsd-hackers@freebsd.org Tue Oct 11 07:14:43 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 6D23BC0D6C1 for ; Tue, 11 Oct 2016 07:14:43 +0000 (UTC) (envelope-from peter@rulingia.com) Received: from vps.rulingia.com (vps.rulingia.com [103.243.244.15]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "mail.rulingia.com", Issuer "Let's Encrypt Authority X3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 00F3DB1F for ; Tue, 11 Oct 2016 07:14:42 +0000 (UTC) (envelope-from peter@rulingia.com) Received: from server.rulingia.com (ppp59-167-167-3.static.internode.on.net [59.167.167.3]) by vps.rulingia.com (8.15.2/8.15.2) with ESMTPS id u9B7EGpL004074 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 11 Oct 2016 18:14:22 +1100 (AEDT) (envelope-from peter@rulingia.com) X-Bogosity: Ham, spamicity=0.000000 Received: from server.rulingia.com (localhost.rulingia.com [127.0.0.1]) by server.rulingia.com (8.15.2/8.15.2) with ESMTPS id u9B7E9dK060849 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Tue, 11 Oct 2016 18:14:10 +1100 (AEDT) (envelope-from peter@server.rulingia.com) Received: (from peter@localhost) by server.rulingia.com (8.15.2/8.15.2/Submit) id u9B7E92B060848; Tue, 11 Oct 2016 18:14:09 +1100 (AEDT) (envelope-from peter) Date: Tue, 11 Oct 2016 18:14:09 +1100 From: Peter Jeremy To: Norbert Koch Cc: freebsd-hackers@freebsd.org Subject: Re: Why at least 4 cylinder groups? Message-ID: <20161011071409.GL76775@server.rulingia.com> References: <201610101526.u9AFQNuH091581@pdx.rh.CN85.dnsmgr.net> <24c7ca75-d50d-a7d2-933b-15ce4cf04b94@demig.de> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="5G06lTa6Jq83wMTw" Content-Disposition: inline In-Reply-To: <24c7ca75-d50d-a7d2-933b-15ce4cf04b94@demig.de> X-PGP-Key: http://www.rulingia.com/keys/peter.pgp User-Agent: Mutt/1.6.1 (2016-04-27) 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: Tue, 11 Oct 2016 07:14:43 -0000 --5G06lTa6Jq83wMTw Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On 2016-Oct-11 08:50:44 +0200, Norbert Koch wrote: >Am 2016-10-10 um 17:26 schrieb Rodney W. Grimes: >>> In an embedded system I am having a rather >>> small (static) ram disk of about 1.5MB, >>> formatted as UFS(1). ufs2 is designed to work around some space limitations in ufs1 and so needs more space. If you're space-limited, ufs1 is probably a better choic= e. >>> Is there any technical reason not to have less >>> than 4 cylinder groups? >> Probably on a UFS2 file system yes, but as far as I can >> see not on a UFS1 file system. >> >>> For my application the wasted 188KB make a difference. =2E.. >So, afaics technically one cylinder group would be ok for UFS1, right? The reasons for multiple CGs are: 1) Improve performance by limiting the seek distance to a CG. 2) Provide redundant superblocks to protect against bad blocks. Neither of these reasons apply to a ramdisk. If you're keen to maximise data space, you might like to also reduce ipg (increase '-i'). --=20 Peter Jeremy --5G06lTa6Jq83wMTw Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQJ8BAEBCgBmBQJX/JFBXxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w ZW5wZ3AuZmlmdGhob3JzZW1hbi5uZXRFRUIyOTg2QzMwNjcxRTc0RTY1QzIyN0Ux NkE1OTdBMEU0QTIwQjM0AAoJEBall6Dkogs0DfsQAJfr2izb/79SFJyitGZq4xal LCF5cvX+1j059fM1k+gZq9XgU1VhZAnr3vjtHzEj6+06YpY77MstoY6Nc+wuv06w xnacU+bxtJLQrhYBg5GemKo4zd1NL79ZizxxTpxRoqoxC3dmTYNMIPxF8kw7J+/w fF0V7cLyUcnIQtcMb3RDc0Db9mQGehZp8qYBwqXuUtrnUQlPWt5z0YxR7m3s+ei5 isq/oi5JV0i95MlelzWbYEe92CMuoPIu4IF8qBUNC45VcOnuif9oZnN+MWVW01gj MIGfStPGjY6hCzfOeogT8welXPrV0Sw/YaG3J0zPewVu/K4bIpYlswkoEOwvoQCj M8qsWn7nlRDFRHMPAeQWUqA6XUnTq+z9zd7HunAyYp3/9VeXk5jKBAcvSGA1q35E tBm3GgPrAUdIup6CHwKrGa+0tmFAj3jBLjuqz2fIOMedqJvEdV5Qel5cuL5In74f z6TjffsdBJQ0IRfVqnP2x6SOuAyRNnu4GnTmH/46rNONPoC8yi7/YE2/A1ByAnFg NsDD6AjiRAWDDwsj01wapBlpe7H8z99UikLv5PE1lY1ohIcydZN5MFfQxQNlYuhb HTIft9iRamp/6u7Q7BqLggou9UyMPy1ZhMqj3Sb26tP9BcsAwhGGttBU6CN4fmXz 6IZbv/CaXb4ggjwGfzH4 =BQOz -----END PGP SIGNATURE----- --5G06lTa6Jq83wMTw--