From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Thu, 4 Jan 2001 15:35:01 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Thu, 4 Jan 2001 15:34:51 -0500 Received: from Cantor.suse.de ([194.112.123.193]:22538 "HELO Cantor.suse.de") by vger.kernel.org with SMTP id ; Thu, 4 Jan 2001 15:34:41 -0500 Date: Thu, 4 Jan 2001 21:31:46 +0100 (CET) From: egger@suse.de Reply-To: egger@suse.de Subject: Re: Journaling: Surviving or allowing unclean shutdown? To: root@chaos.analogic.com Cc: linux-kernel@vger.kernel.org In-Reply-To: MIME-Version: 1.0 Content-Type: TEXT/plain; charset=us-ascii Message-Id: <20010104213355.707A651AA@Nicole.muc.suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On 4 Jan, Richard B. Johnson wrote: > A mobile-phone that runs out of battery power will also lose all the > phone numbers you have stored, etc. The same is true for most all > embedded systems that save data. In your world maybe. I would be quite pissed if my mobile phones lost the stored numbers every time they run out of power. Nearly all embedded devices nowadays keep their settings without power; be it a satellite receiver, a PBX, a fax machine or a coffee brewer. > This means that the data-base > software has to roll-back and redo the temporarily-lost updates > when it restarts. It uses the journal to accomplish this. As > N-seconds gets smaller, the overhead necessary to maintain data > consistency gets greater, so there are trade-offs. And depending on the application they may really be worth it. > A journaling file-system also needs some number to show the > order of operations so that roll-backs and restarts work. > Unfortunately, the systems that I have seen all use time for > the number! You don't want time to reconstruct 'order'. You > need a number that represents 'order'. Time is not your friend. Since the metadata has to be sync anyway what about using a normal transaction counter? -- Servus, Daniel - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org Please read the FAQ at http://www.tux.org/lkml/