Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758830AbZFVVCy (ORCPT ); Mon, 22 Jun 2009 17:02:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758795AbZFVVCi (ORCPT ); Mon, 22 Jun 2009 17:02:38 -0400 Received: from atrey.karlin.mff.cuni.cz ([195.113.26.193]:42459 "EHLO atrey.karlin.mff.cuni.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758786AbZFVVCg (ORCPT ); Mon, 22 Jun 2009 17:02:36 -0400 Date: Mon, 22 Jun 2009 23:02:31 +0200 From: Pavel Machek To: Tim Bird Cc: Marco Stornelli , Jamie Lokier , Linux Embedded , Linux Kernel , Linux FS Devel , Daniel Walker Subject: Re: [PATCH 00/14] Pramfs: Persistent and protected ram filesystem Message-ID: <20090622210231.GC24236@elf.ucw.cz> References: <20090613155957.GA16220@shareable.org> <4A34A394.5040509@gmail.com> <20090621064040.GC1656@ucw.cz> <4A3E6F28.4090404@gmail.com> <20090621205245.GC3254@elf.ucw.cz> <2ea1731b0906212333r20deb71q2f021fc79bcc8a8e@mail.gmail.com> <20090622172003.GB21149@elf.ucw.cz> <4A3FBFF0.40006@am.sony.com> <20090622173704.GC21299@elf.ucw.cz> <4A3FD388.6040801@am.sony.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4A3FD388.6040801@am.sony.com> X-Warning: Reading this can be dangerous to your mental health. User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2350 Lines: 58 On Mon 2009-06-22 11:55:04, Tim Bird wrote: > Pavel Machek wrote: > > On Mon 2009-06-22 10:31:28, Tim Bird wrote: > >> Pavel Machek wrote: > >>> I did not see that in the changelog. If it is not general purpose > >>> filesystem, it is lot less interesting. > >> PRAMFS is not a general purpose filesystem. Please read > >> the introductory post to this thread, or look at > >> http://pramfs.sourceforge.net/ for more information. > > > > Yeah, I seen that. It directly contradicts what you say. > > Could you be more specific? In what way does the > description on the website contradict what I said? You are saying top goal is robustness, while the web page says (home page, stop using frames!): "embedded systems have a block of non-volatile RAM seperate from normal system memory, i.e. of which the kernel maintains no memory page descriptors. For such systems it would be beneficial to mount a fast read/write filesystem over this "I/O memory", for storing frequently accessed data that must survive system reboots and power cycles" Note the "frequently accessed" and "fast". IOW the web page is confusing. It does not talk about robustness at all. > >> Since the purpose of PRAMFS is to provide a filesystem > >> that is persistent across kernel instantions, it is not > >> designed for high speed. Robustness in the face of > >> kernel crashes or bugs is the highest priority, so > >> PRAMFS has significant overhead to make the window > >> of writability to the filesystem RAM as small as possible. > > > > Really? So why don't you use well known, reliable fs like ext3? > > Are you sure you read the web site? It directly addresses this > question. From the web site: "1. Disk-based filesystems such as No, it does not. It explains that ext2 would be too slow on this, and explains that it will eat too much disk space. Please back that claims with numbers. If reliability is top concern, explain how you get away w/o journalling. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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/