From mboxrd@z Thu Jan 1 00:00:00 1970 From: Adam Goryachev Subject: Re: RAID performance Date: Thu, 07 Feb 2013 21:12:10 +1100 Message-ID: <51137DFA.5020406@websitemanagers.com.au> References: <51134E43.7090508@websitemanagers.com.au> <5113516C.5080606@aei.mpg.de> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <5113516C.5080606@aei.mpg.de> Sender: linux-raid-owner@vger.kernel.org To: Carsten Aulbert Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 07/02/13 18:02, Carsten Aulbert wrote: > Hi Adam > > On 02/07/2013 07:48 AM, Adam Goryachev wrote: >> >> Each drive only has a single partition, and is partitioned a little >> smaller than the drive (supposedly this should improve performance). >> Each drive is set to the deadline scheduler. > > First, I'd start with the deadline scheduler. Already using it, am going to try noop shortly.... > Even for rotating rust systems you can improve performance quite a bit, > but with SSDs you might hit the limits way too early and need to tune it. > > Save the current default values somewhere safe, so you can go back > easily, then start tuning these values (as a start): > > for i in $(grep \^md /proc/mdstat |cut -d' ' -f 5-); do > DEV=${i:0:3} > echo deadline > /sys/block/$DEV/queue/scheduler > echo 4096 > /sys/block/$DEV/queue/nr_requests > echo 8192 > /sys/block/$DEV/queue/read_ahead_kb > echo 5000 > /sys/block/$DEV/queue/iosched/read_expire > echo 1000 > /sys/block/$DEV/queue/iosched/write_expire > echo 2048 > /sys/block/$DEV/queue/iosched/fifo_batch > done > > At least setting these helped quite a bit. Do you have any information on what your workload is, or how/why these values might help? You are changing values significantly from the default, and I am cautious that they may cause other issues. Also, someone else has advised to reduce nr_requests rather than increasing it? Thank you for your advice. Regards, Adam -- Adam Goryachev Website Managers www.websitemanagers.com.au