Return-Path: X-Sieve: cmu-sieve 2.0 Return-Path: Received: (from majordom@localhost) by ece.cmu.edu (8.11.0/8.10.2) id h3I2nYU27358 for ips-outgoing; Thu, 17 Apr 2003 22:49:34 -0400 (EDT) X-Authentication-Warning: ece.cmu.edu: majordom set sender to owner-ips@ece.cmu.edu using -f Received: from leviathan.ele.uri.edu (leviathan.ele.uri.edu [131.128.51.64]) by ece.cmu.edu (8.11.0/8.10.2) with ESMTP id h3I2nU327353 for ; Thu, 17 Apr 2003 22:49:30 -0400 (EDT) Received: from dragonfly (ip68-9-255-122.ri.ri.cox.net [68.9.255.122]) by leviathan.ele.uri.edu (8.12.6/8.12.6) with ESMTP id h3I2nRf2015236; Thu, 17 Apr 2003 22:49:28 -0400 (EDT) From: mingz Reply-To: mingz@ele.uri.edu To: David Woolf Subject: Re: iSCSI read/write cost difference Date: Thu, 17 Apr 2003 22:48:40 -0400 User-Agent: KMail/1.5 References: <200304171210.21223.mingz@ele.uri.edu> In-Reply-To: Cc: ips@ece.cmu.edu MIME-Version: 1.0 Content-Type: text/plain; charset="gb2312" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200304172248.40859.mingz@ele.uri.edu> Sender: owner-ips@ece.cmu.edu Precedence: bulk yes, i test these three situations and get the results as follows 1) for all InitialR2T =Y/N, ImmediateData = Y/N, the read results are all same. 2) initialr2t has no influence on write 3) immediatedata has influence on write. IOPS: (scsi ram disk) 2k 4k 8k 16k 32k read 1975 1781 1557 1081 767 write 2877 2225 1588 812 533 (immediatedata =yes) write 1971 1527 1199 880 566 (immediatedata =no) when immediaredata=yes, for small write, data go with the command, so should be faster, but why with large data size, like 16k and 32k, the write is slower? and why write is always slower than read with large data size? btw, can u answer this question, 'Also, does the target piggyback SCSI Response in the Final Datain pdu?' since this code is from your unh iol, hehe. thx. On Thursday 17 April 2003 14:19, you wrote: > Hello, > Have you done these experiments with InitialR2T=Yes and Immediatedata=No, > InitialR2T=Yes and Immediatedata=Yes, and InitialR2T=No and > ImmediateData=Yes? I'd be interested to see how the results change. > > thanks, > > David Woolf > ************************************************ > University of New Hampshire Interoperability Lab > iSCSI and Fibre Channel Consortiums > Durham, NH 03824 > (603) 862 0701 > ************************************************ > > On Thu, 17 Apr 2003, mingz wrote: > > I recently did some experiments on iSCSI benchmarking. I used the UNH > > iSCSi ref18_03 implementation and use a ram based scsi device for iscsi > > target use. so there is no any disk overhead. > > > > I used a linux kernel module to send fixed size read/write requests to > > iscsi initiator, which eventually will be filled by iscsi target. i use > > interl pro1000 gigabit nic and intel 470 gigabit switch. and both > > initiator and target use same type piii 866 pc with 1g ram. > > > > now the IOPS result shows that > > > > 2k 4k 8k 16k 32k > > read 1975 1781 1557 1081 767 > > write 2877 2225 1588 812 533 > > > > for small reuqests, read is slower than write, while for large requests, > > read is faster than write. i redo the experiments on another enviroment, > > also get similar results. > > > > can anybody explain why this happens? > > > > thanks a lot. > > > > > > ming -- -------------------------------------------------- | Ming Zhang, PhD. Student | Dept. of Electrical & Computer Engineering | College of Engineering | University of Rhode Island | Kingston RI. 02881 | e-mail: mingz@ele.uri.edu | Tel. (401) 874-2293 Fax (401) 782-6422 | http://www.ele.uri.edu/~mingz --------------------------------------------------