From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wes Subject: Re: raid10 centos5 vs. centos6 300% worse random write performance Date: Mon, 12 Aug 2013 08:43:13 +0000 (UTC) Message-ID: References: <51F4B034.3040801@hardwarefreak.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Stan Hoeppner hardwarefreak.com> writes: > ~$ cat /sys/block/sda/queue/scheduler > [CFQ] noop deadline > Wes, yours will show CFQ probably as the default on RHEL/CentOS. You'll > want deadline for best seek and all around performance. So: > ~$ echo deadline > /sys/block/sda/queue/scheduler > Add that to an init script or cron entry so it sets on every boot. > Barriers are not an issue with this test. > Thank you all. The issue is now closed. RHEL5 was not doing cache flush right. It was only corrected in 2.6.32+ After removing O_SYNC from seekmark the results are now comparable. Actually it is hard to find a linux raw device random R/W benchmark tool and seekmark being the most popular fails when comparing pre and post 2.6.32 systems (unless you remove O_SYNC).