From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757929AbXGVOEL (ORCPT ); Sun, 22 Jul 2007 10:04:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751363AbXGVOD7 (ORCPT ); Sun, 22 Jul 2007 10:03:59 -0400 Received: from aug.linbit.com ([212.69.162.22]:44554 "EHLO mail.linbit.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751348AbXGVOD6 (ORCPT ); Sun, 22 Jul 2007 10:03:58 -0400 Date: Sun, 22 Jul 2007 16:03:57 +0200 From: Lars Ellenberg To: Jan Engelhardt Cc: Jens Axboe , Andrew Morton , lkml Subject: Re: [DRIVER SUBMISSION] DRBD wants to go mainline Message-ID: <20070722140357.GB32371@mail.linbit.com> References: <20070721203819.GA10706@mail.linbit.com> <20070721224300.GB18326@mail.linbit.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jul 22, 2007 at 11:06:59AM +0200, Jan Engelhardt wrote: > > On Jul 22 2007 00:43, Lars Ellenberg wrote: > >On Sat, Jul 21, 2007 at 11:17:43PM +0200, Jan Engelhardt wrote: > >> On Jul 21 2007 22:38, Lars Ellenberg wrote: > >> > > >> >We implement shared-disk semantics in a shared-nothing cluster. > >> > >> If nothing is shared, the disk is not shared, but got shared-disk > >> semantics? A little confusing. > > > >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) DRBD has built-in logic to track which copy of the data is the most recent. DRBD has resource-level-fencing in place (though we can improve on that). DRBD deals with concurrent writes of the participating nodes correctly. "N-disk" is not the question, you can stack drbd on top of md, lvm, anything. N-nodes is the interessting thing. -- : Lars Ellenberg Tel +43-1-8178292-0 : : LINBIT Information Technologies GmbH Fax +43-1-8178292-82 : : Vivenotgasse 48, A-1120 Vienna/Europe http://www.linbit.com :