From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756336AbZECOi4 (ORCPT ); Sun, 3 May 2009 10:38:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756035AbZECOii (ORCPT ); Sun, 3 May 2009 10:38:38 -0400 Received: from mail.lang.hm ([64.81.33.126]:42616 "EHLO bifrost.lang.hm" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756264AbZECOih (ORCPT ); Sun, 3 May 2009 10:38:37 -0400 Date: Sun, 3 May 2009 07:36:36 -0700 (PDT) From: david@lang.hm X-X-Sender: dlang@asgard To: James Bottomley cc: Willy Tarreau , Bart Van Assche , Andrew Morton , Philipp Reisner , linux-kernel@vger.kernel.org, Jens Axboe , Greg KH , Neil Brown , Sam Ravnborg , Dave Jones , Nikanth Karthikesan , Lars Marowsky-Bree , Kyle Moffett , Lars Ellenberg Subject: Re: [PATCH 00/16] DRBD: a block device for HA clusters In-Reply-To: <1241360474.5596.4.camel@mulgrave.int.hansenpartnership.com> Message-ID: References: <1241090812-13516-1-git-send-email-philipp.reisner@linbit.com> <20090501015902.ed8b56d3.akpm@linux-foundation.org> <20090503053557.GH570@1wt.eu> <1241360474.5596.4.camel@mulgrave.int.hansenpartnership.com> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; format=flowed; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 3 May 2009, James Bottomley wrote: > Subject: Re: [PATCH 00/16] DRBD: a block device for HA clusters > > On Sat, 2009-05-02 at 22:40 -0700, david@lang.hm wrote: >> On Sun, 3 May 2009, Willy Tarreau wrote: >> >>> On Sat, May 02, 2009 at 09:33:35AM +0200, Bart Van Assche wrote: >>>> On Fri, May 1, 2009 at 10:59 AM, Andrew Morton >>>> wrote: >>>>> On Thu, 30 Apr 2009 13:26:36 +0200 Philipp Reisner wrote: >>>>> >>>>>> This is a repost of DRBD >>>>> >>>>> Is it being used anywhere for anything? If so, where and what? >>>> >>>> One popular application is to run iSCSI and HA software on top of DRBD >>>> in order to build a highly available iSCSI storage target. >>> >>> Confirmed, I have several customers who're doing exactly that. >> >> I will also say that there are a lot of us out here who would have a use >> for DRDB in our HA setups, but have held off implementing it specificly >> because it's not yet in the upstream kernel. > > Actually, that's not a particularly strong reason because we already > have an in-kernel replicator that has much of the functionality of drbd > that you could use. The main reason for wanting drbd in kernel is that > it has a *current* user base. > > Both the in kernel md/nbd and drbd do sync and async replication with > primary side bitmaps. The main differences are: > > * md/nbd can do 1 to N replication, > * drbd can do active/active replication (useful for cluster > filesystems) > * The chunk size of the md/nbd is tunable > * With the updated nbd-tools, current md/nbd can do point in time > rollback on transaction logged secondaries (a BCS requirement) > * drbd manages the mirror state explicitly, md/nbd needs a user > space helper > > And probably a few others I forget. one very big one: DRDB has better support for dealing with split brain situations and recovering from them. David Lang