From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mirko Benz Subject: Re: SATA on mptsas performance Date: Wed, 15 Feb 2006 08:52:07 +0100 Message-ID: <43F2DDA7.7050700@web.de> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from 162.237.ddkom.net ([212.80.237.162]:44216 "EHLO cheetah.dd.xiranet.com") by vger.kernel.org with ESMTP id S1422666AbWBOHwk (ORCPT ); Wed, 15 Feb 2006 02:52:40 -0500 In-Reply-To: Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: "Moore, Eric" Cc: linux-scsi@vger.kernel.org Hello, The SAS3442X is connected to the JBOD via a x4 SAS cable. The JBOD has an LSI SAS Expander chip - no port multiplier. Disks are Seagate ST3300831AS (300 GB, SATA-I, NCQ) Does the SAS controller and the SAS expander communicate at 3 Gb when accessing SATA disks? If not it should give 4 * 150 MB/s r/w throughput for this configuration. I am testing with parallel dd invocations on the raw device e.g.: dd if=/dev/sdb of=/dev/null bs=32k count=10000 & ... dd if=/dev/sdl of=/dev/null bs=32k count=10000 & I have tested with IOMETER but the results are worse. I will test SATA II disks later. But I assume there is a scheduling problem (mapping 10 disks to 4 channels). The CPU load is also very high. Disks support NCQ but it should have no effect due to sequential access of a single application per disk. How to switch on/off NCQ? Regards, Mirko