From owner-freebsd-stable@FreeBSD.ORG Wed Oct 24 13:16:54 2007 Return-Path: Delivered-To: freebsd-stable@FreeBSD.ORG Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 3AEA116A421; Wed, 24 Oct 2007 13:16:54 +0000 (UTC) (envelope-from olli@lurza.secnetix.de) Received: from lurza.secnetix.de (lurza.secnetix.de [IPv6:2001:1b20:1:3::1]) by mx1.freebsd.org (Postfix) with ESMTP id A5CD613C4A5; Wed, 24 Oct 2007 13:16:53 +0000 (UTC) (envelope-from olli@lurza.secnetix.de) Received: from lurza.secnetix.de (localhost [127.0.0.1]) by lurza.secnetix.de (8.14.1/8.14.1) with ESMTP id l9ODGYXJ093702; Wed, 24 Oct 2007 15:16:41 +0200 (CEST) (envelope-from oliver.fromme@secnetix.de) Received: (from olli@localhost) by lurza.secnetix.de (8.14.1/8.14.1/Submit) id l9ODGYfZ093701; Wed, 24 Oct 2007 15:16:34 +0200 (CEST) (envelope-from olli) Date: Wed, 24 Oct 2007 15:16:34 +0200 (CEST) Message-Id: <200710241316.l9ODGYfZ093701@lurza.secnetix.de> From: Oliver Fromme To: freebsd-stable@FreeBSD.ORG, freebsd-fs@FreeBSD.ORG, freebsd-current@FreeBSD.ORG, amdmi3@amdmi3.ru In-Reply-To: X-Newsgroups: list.freebsd-stable User-Agent: tin/1.8.3-20070201 ("Scotasay") (UNIX) (FreeBSD/6.2-STABLE-20070808 (i386)) MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-2.1.2 (lurza.secnetix.de [127.0.0.1]); Wed, 24 Oct 2007 15:16:42 +0200 (CEST) Cc: Subject: Re: [ANN] 8-CURRENT, RELENG_7 and RELENG_6 have gotten latest ?unionfs improvements X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: freebsd-stable@FreeBSD.ORG, freebsd-fs@FreeBSD.ORG, freebsd-current@FreeBSD.ORG, amdmi3@amdmi3.ru List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 24 Oct 2007 13:16:54 -0000 [Note: stripped excessive Cc.] Dmitry Marakasov wrote: > Btw, I was wondering: is unionfs related in any way with -ounion > option of mount_*? No. The union mount option (-o union) is completely separate from UNIONFS, although it can be used to achieve a somewhat similar effect. It depends on your requirements whether it is sufficient or not. > I was told long time ago that -ounion is even > more broken than unionfs. That's wrong. The union mount option was _never_ really broken. I'm using it for almost as long as FreeBSD exists. However UNIONFS was broken for a long time (along with NULLFS and UMAPFS). NULLFS has been fixed some time ago, UMAPFS was abandoned apparently, i.e. nobody showed up to fix it, and UNIONFS was pretty much completely overhauled by Daichi GOTO and his team. I would now regard it as stable. > Though, those two features seem to do very > similar thing and I think that -ounion option is pretty useful. Yes, it is useful. The biggest differences are: - The union mount option newly mounts a filesystem on top of an arbitrary existing directory tree, while UNIONFS mounts another representation of one existing directory tree on top of another one. That means UNIONFS does the same as NULLFS, but unlike NULLFS it does not hide the underlying directory tree. - When using the union mount option, only the entries in the root directory show through from the "lower" file system. When using UIONFS, _all_ entries in _all_ directories are visible (unless masked by an identical entry in the upper file system, of course). - The implementation of the union mount option is rather simple has rather low overhead. UNIONFS is much more complex and has some overhead for certain operations, especially when files and directories have to be created automatically in the upper layer. Best regards Oliver -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing b. M. Handelsregister: Registergericht Muenchen, HRA 74606, Geschäftsfuehrung: secnetix Verwaltungsgesellsch. mbH, Handelsregister: Registergericht Mün- chen, HRB 125758, Geschäftsführer: Maik Bachmann, Olaf Erb, Ralf Gebhart FreeBSD-Dienstleistungen, -Produkte und mehr: http://www.secnetix.de/bsd "Python is an experiment in how much freedom programmers need. Too much freedom and nobody can read another's code; too little and expressiveness is endangered." -- Guido van Rossum