From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladislav Bolkhovitin Subject: Re: Performance of SCST versus STGT Date: Thu, 24 Jan 2008 14:10:06 +0300 Message-ID: <4798720E.4020802@vlnb.net> References: <20080117184052F.fujita.tomonori@lab.ntt.co.jp> <478F246C.4040400@vlnb.net> <20080117190558K.fujita.tomonori@lab.ntt.co.jp> <20080117174542.GC29650@osc.edu> <4795D4A7.5000105@vlnb.net> <20080124070616.GA31633@porcupine.cita.utoronto.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-relay-01.mailcluster.net ([77.221.130.213]:34881 "EHLO mail-relay-01.mailcluster.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752397AbYAXLJ7 (ORCPT ); Thu, 24 Jan 2008 06:09:59 -0500 In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Bart Van Assche Cc: Robin Humble , FUJITA Tomonori , stgt-devel@lists.berlios.de, linux-scsi@vger.kernel.org, James.Bottomley@hansenpartnership.com, scst-devel@lists.sourceforge.net Bart Van Assche wrote: > On Jan 24, 2008 8:06 AM, Robin Humble wrote: > >>On Tue, Jan 22, 2008 at 01:32:08PM +0100, Bart Van Assche wrote: >> >>>............................................................................................. >>>. . STGT read SCST read . STGT read SCST read . >>>. . performance performance . performance performance . >>>. . (0.5K, MB/s) (0.5K, MB/s) . (1 MB >MB/s) (1 MB, MB/s) . >>>............................................................................................. >>>. Ethernet (1 Gb/s network) . 77 78 . 77 89 . >>>. IPoIB (8 Gb/s network) . 163 185 . 201 239 . >>>. iSER (8 Gb/s network) . 250 N/A . 360 N/A . >>>. SRP (8 Gb/s network) . N/A 421 . N/A 683 . >>>............................................................................................ >> >>how are write speeds with SCST SRP? >>for some kernels and tests tgt writes at >2x the read speed. Robin, There is a fundamental difference between regular dd-like reads and writes: reads are sync, i.e. latency sensitive, but writes are async, i.e. latency insensitive. You should use O_DIRECT dd writes for the fair comparison. Vlad