From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark Lehrer Subject: megaraid_sas (H710), fast SSD's, poor RAID0 performance Date: Mon, 25 Mar 2013 09:57:40 -0600 (MDT) Message-ID: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; format=flowed; charset=US-ASCII Return-path: Received: from knm.org ([173.10.24.5]:47888 "EHLO knm.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932231Ab3CYQ6Y (ORCPT ); Mon, 25 Mar 2013 12:58:24 -0400 Received: from [192.168.20.65] (account mark@knm.org HELO shell) by knm.org (CommuniGate Pro SMTP 5.4.8 _community_) with ESMTPSA id 9137895 for linux-scsi@vger.kernel.org; Mon, 25 Mar 2013 09:57:40 -0600 Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: linux-scsi@vger.kernel.org Hello there, I have a server in our test lab (specs below) that doesn't appear to be getting nearly the write speeds that I was expecting (test details below). In "top" terminology, there is one CPU core at about 30% SI and each core shows anywhere from 1 to 15 % SY and about the same for WA. My main question: what tools do I need to get some visibility as to what is going on within the megaraid_sas module and on the SAS controller itself? I have gone about as far as I can go with utilities such as top and MegaCli. For simplicity, I am only focusing on raw write speed straight to the block device. I have a few benchmarks I use, mainly Orion and some of the Phoronix suite, but Currently the easiest test is just: dd if=/dev/zero of=/dev/sdc ibs=1048576 obs=1048576 The main symptom is that with a single disk I can push > 300MB/sec, and with a pair in RAID0 I can get over 600MB/sec, but with 5 of these in RAID0 it never goes above around 700MB/sec. My next test will be to use each disk as a separate device and try software raid (or just writing to each disk simultaneously). Thanks, Mark p.s. system specs: Dell 720xd, H710 ("mini") controller 5x Micron P300 SATA SLC SSD's