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 00F992E29485 for ; Wed, 11 Apr 2007 17:01:49 +0200 (CEST) Received: from paraoa.dcs.gla.ac.uk ([130.209.253.109]:58214) by mr1.dcs.gla.ac.uk with esmtpa (Exim 4.42) id 1HbeKT-00022e-6l for drbd-dev@lists.linbit.com; Wed, 11 Apr 2007 16:01:49 +0100 Message-ID: <461CF901.70008@dcs.gla.ac.uk> Date: Wed, 11 Apr 2007 16:04:33 +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> <461CE69A.5020604@dcs.gla.ac.uk> <20070411145140.GA4659@barkeeper1.linbit> In-Reply-To: <20070411145140.GA4659@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 02:46:02PM +0100, Cristian Zamfir wrote: >> 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? > > and your exact bonnie++ command line is: > Bonnie++ is run with the default parameters: bonnie++ -u zamf -d bonnie/ I have results from ./tiobench, with shows a 2.4x increase in performance in favour of protocol A: /usr/bin/tiotest -t 8 -f 60 -r 500 -b 4096 -d . -T-T Protocol A Sequential Writes File Blk Num Avg Maximum Lat% Lat% CPU Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff ---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- ----- 2.6.18-xenU 480 4096 1 24.27 11.73% 0.126 724.87 0.00000 0.00000 207 2.6.18-xenU 480 4096 2 20.32 10.07% 0.312 1002.72 0.00000 0.00000 202 2.6.18-xenU 480 4096 4 16.57 7.733% 0.648 4505.20 0.00570 0.00000 214 2.6.18-xenU 480 4096 8 15.96 7.445% 1.107 6598.77 0.02279 0.00000 214 Protocol C Sequential Writes File Blk Num Avg Maximum Lat% Lat% CPU Identifier Size Size Thr Rate (CPU%) Latency Latency >2s >10s Eff ---------------------------- ------ ----- --- ------ ------ --------- ----------- -------- -------- ----- 2.6.18-xenU 480 4096 1 10.46 5.032% 0.301 1232.91 0.00000 0.00000 208 2.6.18-xenU 480 4096 2 10.74 5.032% 0.581 1981.85 0.00000 0.00000 213 2.6.18-xenU 480 4096 4 10.55 5.009% 0.849 3782.22 0.01302 0.00000 211 2.6.18-xenU 480 4096 8 10.32 4.923% 1.841 8250.74 0.03581 0.00000 210