From mboxrd@z Thu Jan 1 00:00:00 1970 From: keld@keldix.com Subject: Re: RAID 10 / 2 Devices Layout question Date: Tue, 28 Jun 2016 14:40:17 +0200 Message-ID: <20160628124017.GA7953@www5.open-std.org> References: <5770120D.9050809@turmel.org> <20160628142502.7e69983d@natsu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20160628142502.7e69983d@natsu> Sender: linux-raid-owner@vger.kernel.org To: Roman Mamedov Cc: Phil Turmel , Paul Roland , linux-raid@vger.kernel.org List-Id: linux-raid.ids On Tue, Jun 28, 2016 at 02:25:02PM +0500, Roman Mamedov wrote: > On Sun, 26 Jun 2016 13:34:05 -0400 > Phil Turmel wrote: > > > On 06/26/2016 01:20 PM, Paul Roland wrote: > > > > > I have two SSDs, and I would like to use md/raid10 (2devices) for > > > performance reasons. > > > > Ok, that's reasonable. > > Maybe I'm missing something, but how is a RAID10 of just two devices is > considered reasonable without any questions or explanation? What is the actual > layout that is expected here, and what benefits (or even differences) does it > have compared to RAID0? I thought you need at least 3 devices (and h/w RAID > controllers might even require 4) for RAID10 to start making sense. I think your understanding is a common misunderstanding of the Linux raid10. There is more on this subject on: https://en.wikipedia.org/wiki/Non-standard_RAID_levels#Linux_MD_RAID_10 In short: yes Linux MD RAID10 is a different beast than standard RAID 1+0, It can work with improved performance with just 2 disks, and even perform like RAID0 for the Linux MD RAID10 far layout See more on https://raid.wiki.kernel.org/index.php/Performance best regards Keld