From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mr1.dcs.gla.ac.uk (mr1.dcs.gla.ac.uk [130.209.249.184]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mail.linbit.com (LINBIT Mail Daemon) with ESMTP id AF0702E2716C for ; Wed, 11 Apr 2007 15:43:18 +0200 (CEST) Received: from paraoa.dcs.gla.ac.uk ([130.209.253.109]:55324) by mr1.dcs.gla.ac.uk with esmtpa (Exim 4.42) id 1Hbd6U-0007G5-4I for drbd-dev@lists.linbit.com; Wed, 11 Apr 2007 14:43:18 +0100 Message-ID: <461CE69A.5020604@dcs.gla.ac.uk> Date: Wed, 11 Apr 2007 14:46:02 +0100 From: Cristian Zamfir MIME-Version: 1.0 To: drbd-dev@lists.linbit.com Subject: Re: [Drbd-dev] switching between protocols A and C References: <461CD0EC.4040402@dcs.gla.ac.uk> <20070411125716.GC27110@barkeeper1.linbit> In-Reply-To: <20070411125716.GC27110@barkeeper1.linbit> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit List-Id: Coordination of development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Lars Ellenberg wrote: > On Wed, Apr 11, 2007 at 01:13:32PM +0100, Cristian Zamfir wrote: >> Hi, >> >> Would it be possible to switch from protocol A to C and vice versa >> without disconnecting (for instance detach, switch protocol and re-attach)? >> >> This would be useful when alternating between two primaries (only >> protocol C can be used) and a primary/secondary configuration where >> protocol A may increase write throughput on the primary node. > > protocol A does _NOT_ increase throughput at all. > it _MAY_ reduce latency somewhat sometimes. I am testing with the bonnie++ benchmark over a 100Mbps link and I get a substantial increase for output in the case of protocol A at the expense of higher CPU ratio. From what I understand, it would make sense to get better throughput from the asynchronous protocol over low quality links. Or am I doing something wrong? drbd connected protocol C Version 1.03 ------Sequential Output------ --Sequential Input- --Random- -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP raoul 464M 12764 52 13525 4 8401 0 18724 39 27174 0 198.4 0 ------Sequential Create------ --------Random Create-------- -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 27245 94 +++++ +++ 27305 99 26368 98 +++++ +++ 22775 95 raoul,464M,12764,52,13525,4,8401,0,18724,39,27174,0,198.4,0,16,27245,94,+++++,+++,27305,99,26368,98,+++++,+++,22775,95 drbd connected protocol A Version 1.03 ------Sequential Output------ --Sequential Input- --Random- -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks-- Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec %CP raoul 464M 27292 90 33632 10 11140 0 19785 46 28524 0 218.0 0 ------Sequential Create------ --------Random Create-------- -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete-- files /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP /sec %CP 16 27136 97 +++++ +++ 26985 100 26775 98 +++++ +++ 23972 100 raoul,464M,27292,90,33632,10,11140,0,19785,46,28524,0,218.0,0,16,27136,97,+++++,+++,26985,100,26775,98,+++++,+++,23972,100 > >> Right now this behaviour does not seem to be supported but I am >> interested if you consider it could be implemented easily. > > no. and it does not make much sense for me, either. > Cristian