From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladislav Bolkhovitin Subject: Re: Integration of SCST in the mainstream Linux kernel Date: Tue, 05 Feb 2008 22:02:16 +0300 Message-ID: <47A8B2B8.2020108@vlnb.net> References: <47A89889.9060701@Voltaire.COM> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-relay-02.mailcluster.net ([77.221.130.214]:56417 "EHLO mail-relay-02.mailcluster.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756123AbYBETCN (ORCPT ); Tue, 5 Feb 2008 14:02:13 -0500 In-Reply-To: <47A89889.9060701@Voltaire.COM> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Erez Zilber Cc: Bart Van Assche , FUJITA Tomonori , linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, James.Bottomley@hansenpartnership.com, scst-devel@lists.sourceforge.net, Andrew Morton , Linus Torvalds Erez Zilber wrote: > Bart Van Assche wrote: > >>As you probably know there is a trend in enterprise computing towards >>networked storage. This is illustrated by the emergence during the >>past few years of standards like SRP (SCSI RDMA Protocol), iSCSI >>(Internet SCSI) and iSER (iSCSI Extensions for RDMA). Two different >>pieces of software are necessary to make networked storage possible: >>initiator software and target software. As far as I know there exist >>three different SCSI target implementations for Linux: >>- The iSCSI Enterprise Target Daemon (IETD, >>http://iscsitarget.sourceforge.net/); >>- The Linux SCSI Target Framework (STGT, http://stgt.berlios.de/); >>- The Generic SCSI Target Middle Level for Linux project (SCST, >>http://scst.sourceforge.net/). >>Since I was wondering which SCSI target software would be best suited >>for an InfiniBand network, I started evaluating the STGT and SCST SCSI >>target implementations. Apparently the performance difference between >>STGT and SCST is small on 100 Mbit/s and 1 Gbit/s Ethernet networks, >>but the SCST target software outperforms the STGT software on an >>InfiniBand network. See also the following thread for the details: >>http://sourceforge.net/mailarchive/forum.php?thread_name=e2e108260801170127w2937b2afg9bef324efa945e43%40mail.gmail.com&forum_name=scst-devel. >> >> > > Sorry for the late response (but better late than never). > > One may claim that STGT should have lower performance than SCST because > its data path is from userspace. However, your results show that for > non-IB transports, they both show the same numbers. Furthermore, with IB > there shouldn't be any additional difference between the 2 targets > because data transfer from userspace is as efficient as data transfer > from kernel space. And now consider if one target has zero-copy cached I/O. How much that will improve its performance? > The only explanation that I see is that fine tuning for iSCSI & iSER is > required. As was already mentioned in this thread, with SDR you can get > ~900 MB/sec with iSER (on STGT). > > Erez