From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Blunck Subject: Re: [RFC 12/26] ext2 white-out support Date: Thu, 2 Aug 2007 14:05:24 +0200 Message-ID: <20070802120524.GY5101@hasse.suse.de> References: <1185997941.18007.30.camel@kleikamp.austin.ibm.com> <200708012206.l71M6ai6028268@agora.fsl.cs.sunysb.edu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Dave Kleikamp , Josef Sipek , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Bharata B Rao , hch@infradead.org To: Erez Zadok Return-path: Received: from mail.suse.de ([195.135.220.2]:34108 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756990AbXHBMFZ (ORCPT ); Thu, 2 Aug 2007 08:05:25 -0400 Content-Disposition: inline In-Reply-To: <200708012206.l71M6ai6028268@agora.fsl.cs.sunysb.edu> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org On Wed, Aug 01, Erez Zadok wrote: > There are three other reasons why Unionfs and our users like to have > multiple writable branches: > ... > And yes, it does make our implementation more complex. And error-prone and unflexible wrt to changes. When XIP was introduced, unionfs crashed all over this changes. I don't know if this has changed yet. Not speaking of other issues like calling back into VFS (stack usage), locking problems and so on. > 3. Some people use Unionfs in the scenario described in point #2 above, as a > poor man's space- and load- distribution system. Some of our users like > the idea of controlling how much storage space they give each branch, and > how much it might grow, and even how much CPU or I/O load might be placed > on each of the lower filesystems which serve a given branch. That way > they worry less about the top-layer's space filling up more quickly than > expected. Now Unionfs was never designed to be a load-balancing f/s (we > have RAIF for that, see ), > but users seems to always find creative ways to [ab]use one's software in > ways one never thought of. :-) And this has nothing to do with unioning ... > BTW, does Union Mounts copyup on meta-data changes (e.g., chmod, chgrp, > etc.)? No. But it was proposed during on of the last postings.