From mboxrd@z Thu Jan 1 00:00:00 1970 From: EJ Vincent Subject: Re: Suboptimal raid6 linear read speed Date: Wed, 16 Jan 2013 15:40:11 -0500 Message-ID: <50F7102B.3030307@ejane.org> References: <20130115123301.GA11948@rabbit.us> <50F55046.7050605@turmel.org> <20130115125507.GA12184@rabbit.us> <20130115170937.GA8831@kevin> <20130115195707.GA30921@www5.open-std.org> <20130116044335.GA10165@kevin> <20130116093651.GB1069@www5.open-std.org> <20130116160957.GB10165@kevin> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130116160957.GB10165@kevin> Sender: linux-raid-owner@vger.kernel.org Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 1/16/2013 11:09 AM, Charles Polisher wrote: > keld@keldix.com wrote: >> Hi Charles >> >> It really does not show below which layout you use for RAID10. This is quite >> important as the different layouts of RAID10 have quite different >> performance characteristics. The 'far' layout tends to be the fastest. >> Which command did you use to create the RAID10 array? > > > mdadm --create /dev/md1 --chunk=64 --level=10 \ > --raid-devices=8 --spare-devices=0 \ > --parity=n2 \ > /dev/sd[abcdefgh]1 > >>> # cat /proc/mdstat >>> Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] [multipath] >>> md1 : active raid10 sdi[7] sdh[6] sdg[5] sdf[4] sde[3] sdd[2] sdc[1] sdb[0] >>> 2118656 blocks 64K chunks 2 near-copies [8/8] [UUUUUUUU] > ^^^^^^^^^^^^^ > I will be testing far placement as well. > > I very much appreciate your interest and guidance. To clarify my > goals, I am trying to demonstrate generalized RAID charac- > teristics using an experimental workbench in various config- > urations, tying the observed experimental data to expected > values. I'd like to wring out obvious errors in my experimental > technique. > > The initial motivation was a glaringly poor choice of RAID level > for a performance-sensitive production system which I have to > live with for years to come. The most unsettling aspect was that > the selection process was stymied by the complexity of the > choices and an abundance of disinformation. I want to address > this pitfall by publishing an illustrated guide to performance, > cost, and reliability up and down the storage stack, helping > people to make reasoned choices in purchasing and configuring > storage. Varying the RAID level and configuration are key (but > not the only) parts of this work. I'm well along in the > literature search, workbench setup, and toolchain. I'm expecting > to put a year or two into the project and to open source > everything. > > Best regards, I am excited to see the results of this project. Good luck! I'll be waiting patiently. -- EJ Vincent ej@ejane.org