From mboxrd@z Thu Jan 1 00:00:00 1970 From: john clyne Subject: Re: IO transfer limits Date: Wed, 10 Jan 2007 15:07:01 -0800 (PST) Message-ID: <8268682.post@talk.nabble.com> References: <8260533.post@talk.nabble.com> <45A53290.1060400@torque.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Received: from www.nabble.com ([72.21.53.35]:38145 "EHLO talk.nabble.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965198AbXAJXHD (ORCPT ); Wed, 10 Jan 2007 18:07:03 -0500 Received: from [72.21.53.38] (helo=jubjub.nabble.com) by talk.nabble.com with esmtp (Exim 4.50) id 1H4mX7-0001Pv-9D for linux-scsi@vger.kernel.org; Wed, 10 Jan 2007 15:07:01 -0800 In-Reply-To: <45A53290.1060400@torque.net> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: linux-scsi@vger.kernel.org So given that the HBA max_sectors_kb looks sufficiently large, my interpretation of your article is the next place I need to look is at ajusting SCSI_MAX_PHYS_SEGMENTS. Sounds like i can only increase this to 256. Does that than give me a max transfer size of 256 * page_size (4k) = 1MB? Is 1MB the limit or am I missing something? thanks - jc Douglas Gilbert wrote: > > john clyne wrote: >> Can anyone give me some guidance on where in the IO stack I might be >> running >> into a 512KB limit on IO transfer sizes to an external FC device? I've >> checked IO scheduler parameter >> (/sys/block//queue/{max_sectors_kb,max_hw_sectors_kb}. Both are set >> to >> 32767. I'm using Qlogic HBAs (qla2312), but I don't see any relevent >> parameters. I'm running RHEL 4.0 with a 2.6.9-34 kernel. Any pointers >> would >> be greatly appreciated. > > John, > I discuss the subject in this page: > http://www.torque.net/sg/sg_io.html > in the section titled: > Maximum transfer size per command > > Mike C. has given you the answer for the block device > interface (e.g. via /dev/sda); you should be able > to do about 8 times better via the scsi generic > interface (e.g. /dev/sg0). > > Doug Gilbert > > > - > To unsubscribe from this list: send the line "unsubscribe linux-scsi" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- View this message in context: http://www.nabble.com/IO-transfer-limits-tf2953389.html#a8268682 Sent from the linux-scsi mailing list archive at Nabble.com.