Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Fri, 27 Apr 2001 12:53:39 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Fri, 27 Apr 2001 12:53:30 -0400 Received: from eventhorizon.antefacto.net ([193.120.245.3]:42375 "EHLO eventhorizon.antefacto.net") by vger.kernel.org with ESMTP id ; Fri, 27 Apr 2001 12:53:19 -0400 Message-ID: <3AE9B203.88B6C799@antefacto.com> Date: Fri, 27 Apr 2001 18:53:07 +0100 From: Padraig Brady X-Mailer: Mozilla 4.77 [en] (X11; U; Linux 2.4.0-ac4 i686) X-Accept-Language: en MIME-Version: 1.0 To: linux-kernel@vger.kernel.org Subject: Re: ramdisk/tmpfs/ramfs/memfs ? In-Reply-To: <3AE99CE8.BD325F52@antefacto.com> <15296.988386995@redhat.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org David Woodhouse wrote: > > padraig@antefacto.com said: > > btw I get my initial root filesystem from a compact flash that can be > > accessed just like a hardisk. It's writeable also like a harddisk, but > > we boot with it readonly, and only mount it rw if we want to save > > config or whatever. We definitely wouldn't swap to it as it has > > limited erase/write cycles. The filesystem is compressed ext2. > > Why copy it into RAM? Why not use cramfs and either turn the writable > directories into symlinks into a ramfs which you create at boot time, or > union-mount a ramfs over the top of it? ? I never said I copied it into RAM. The ramfs is just used for /tmp & /var which are symlinks on the flash. I didn't know you could read/write cramfs like ext2/JFFS2? I still want to be able to update/create/delete files like a normal ext2 partition. Oh I see the confusion, sorry my fault, when I said the root filesystem is compressed ext2, I meant it's ext2 with chattr +c done on all files (the e2compr patch implmenents it). By the way why isn't e2compr a standard part of the kernel. I've have no problems at all with it. I didn't know about union-mounting, seems useful. As for whether to use tmpfs/ramfs I think they do basically the same thing only the implementation is different. tmpfs uses shared mem and so is probably more portable than ramfs which it tightly coupled with VFS. I think I'll use ramfs (with limits patch) so. > padraig@antefacto.com said: > > As for using JFFS2 + MTD ramdisk intead of ext2+e2compr+ramdisk is not > > an option as the only advantage would be journalling, you still can't > > resize. IMHO JFFS is only required where you have flash without an IDE > > interface. > > True. We are currently lacking a compact, compressing, journalling > filesystem for use on block devices. It's been suggested that we could make > JFFS2 work on them, by making a fake MTD device which uses a block device > as backing store. Nobody's yet shown me the code though :) How much more efficent is JFFS than say ext3+e3compr, wrt: logic size/logic speed/RAM requirements/filesystem structure size. > -- > dwmw2 Padraig. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/