From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765849AbXGVJy6 (ORCPT ); Sun, 22 Jul 2007 05:54:58 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758284AbXGVJyt (ORCPT ); Sun, 22 Jul 2007 05:54:49 -0400 Received: from mail.syneticon.net ([213.239.212.131]:38709 "EHLO mail2.syneticon.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757273AbXGVJys (ORCPT ); Sun, 22 Jul 2007 05:54:48 -0400 Message-ID: <46A3295D.8050908@wpkg.org> Date: Sun, 22 Jul 2007 11:54:37 +0200 From: Tomasz Chmielewski User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.8) Gecko/20061110 Mandriva/1.5.0.8-1mdv2007.1 (2007.1) Thunderbird/1.5.0.8 Mnenhy/0.7.4.666 MIME-Version: 1.0 To: LKML Cc: jengelh@computergmbh.de Subject: Re: [DRIVER SUBMISSION] DRBD wants to go mainline Content-Type: text/plain; charset=ISO-8859-2; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Jan Engelhardt wrote > On Jul 22 2007 00:43, Lars Ellenberg wrote: >>Think of it as RAID1 over TCP. > > And what does it do better than raid1-over-NBD? (Which is already N-disk, > and, logically, seems to support cluster filesystems) I don't know about DRDB, but NBD doesn't handle network disconnections at all (well, almost). So basically, disconnect a NBD-connected system for a while (switch, cabling problem, operator error etc.), and you need lots of effort, perhaps restarts, to get the things to a functioning state (devices offlined, kicked out etc.). I wouldn't call such raid-over-NBD setup reliable. A better question would be: what does it do better than raid1-over-iSCSI? iSCSI can recover from disconnections very well when configured properly; but when a disconnection is in place, most of the system will just "hang/freeze" (that is, from the user perspective - the system will be waiting for the I/O to complete, until the systems are connected again). A brief reading of "official DRBD FAQ" didn't give me an answer to that problem. -- Tomasz Chmielewski http://wpkg.org