From owner-freebsd-current@FreeBSD.ORG Sun Feb 20 02:06:29 2005 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 6F0D716A4CE for ; Sun, 20 Feb 2005 02:06:29 +0000 (GMT) Received: from srv1.cosmo-project.de (srv1.cosmo-project.de [213.83.6.106]) by mx1.FreeBSD.org (Postfix) with ESMTP id 9C54B43D46 for ; Sun, 20 Feb 2005 02:06:28 +0000 (GMT) (envelope-from ticso@cicely12.cicely.de) Received: from cicely5.cicely.de (cicely5.cicely.de [10.1.1.7]) (authenticated bits=0)j1K26GE1011504 (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=OK); Sun, 20 Feb 2005 03:06:18 +0100 (CET) (envelope-from ticso@cicely12.cicely.de) Received: from cicely12.cicely.de (cicely12.cicely.de [IPv6:3ffe:400:8d0:301::12]) by cicely5.cicely.de (8.12.10/8.12.10) with ESMTP id j1K25R55072028 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Sun, 20 Feb 2005 03:05:27 +0100 (CET) (envelope-from ticso@cicely12.cicely.de) Received: from cicely12.cicely.de (localhost [127.0.0.1]) by cicely12.cicely.de (8.12.11/8.12.11) with ESMTP id j1K25QX7024076; Sun, 20 Feb 2005 03:05:26 +0100 (CET) (envelope-from ticso@cicely12.cicely.de) Received: (from ticso@localhost) by cicely12.cicely.de (8.12.11/8.12.11/Submit) id j1K25QEm024075; Sun, 20 Feb 2005 03:05:26 +0100 (CET) (envelope-from ticso) Date: Sun, 20 Feb 2005 03:05:26 +0100 From: Bernd Walter To: Eric Anderson Message-ID: <20050220020525.GV14312@cicely12.cicely.de> References: <20050216224825.39102.qmail@web26807.mail.ukl.yahoo.com> <4213D046.4080001@centtech.com> <7579f7fb05021715344d661662@mail.gmail.com> <421605D0.80302@centtech.com> <20050218172831.GA9944@freebie.xs4all.nl> <4217BAC5.10504@centtech.com> <20050220000418.GU14312@cicely12.cicely.de> <4217DC90.5090202@centtech.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4217DC90.5090202@centtech.com> X-Operating-System: FreeBSD cicely12.cicely.de 5.2-CURRENT alpha User-Agent: Mutt/1.5.6i X-Spam-Status: No, hits=-4.9 required=3.0 tests=BAYES_00 autolearn=no version=2.64 X-Spam-Report: * -4.9 BAYES_00 BODY: Bayesian spam probability is 0 to 1% * [score: 0.0000] X-Spam-Checker-Version: SpamAssassin 2.64 (2004-01-11) on cicely12.cicely.de cc: Wilko Bulte cc: FreeBSD Current cc: ticso@cicely.de cc: Matthew Jacob Subject: Re: newfs limits? 10TB filesystem max? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list Reply-To: ticso@cicely.de List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 20 Feb 2005 02:06:29 -0000 On Sat, Feb 19, 2005 at 06:40:48PM -0600, Eric Anderson wrote: > Bernd Walter wrote: > >Creating sparse files, e.g. by using dd, is prety much unix basics. > >And via md(4) you can get a disk type device from a file. > > Sorry - I understand how to make a file with dd, but 5000TB filesystem > means to me someone has 5PB of space to put the filesystem on.. I had not > heard anyone call a file a 'sparse file' with regards to dd before this, > and the man page info for dd and sparse isn't all that telling. dd is just a tool to write a single block at a fileoffset. You can also do with truncate - I usually use dd because truncate is not avalable e.g. under Solaris. It an UFS feature to not allocate space for file ranges that have never been writen. A file without continuous space allocation is called a sparse file. > >testdisk=/tmp/testdisk > >dd if=/dev/zero bs=512 count=1 oseek=2m of=${testdisk} > >mdev=`mdconfig -a -t vnode -f ${testdisk}` > > > >I don't know if md(4) works with such large disks, but it's very likely > >that is does. > > I see that running the command gives a 1GB file, that takes very little > disk space. I must have missed this option in the dd man pages, or never > looked for it. However - you need your filesystem setup to support such large files. That is large fragments to allow large allocation chains with big fragments each. In my case I was limited to 128T and since I don't want to newfs the backing filesystem that's my limit for now without concatenating multiple of them. -- B.Walter BWCT http://www.bwct.de bernd@bwct.de info@bwct.de