From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Brown Subject: Re: raid1 mirror optimizations Date: Wed, 26 Jan 2011 22:08:58 +0100 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 26/01/11 17:37, Oliver Brakmann wrote: > On 2011-01-26 16:39, Roberto Spadim wrote: >> i don't know what layout does, but, does raid1 have layout? > > No, only raid10 has different layouts. For an explanation, see David's > mail, or take a look at the Wikipedia entry for non-standard RAID > levels, it illustrates the idea of the different layouts quite well, > IMO: http://en.wikipedia.org/wiki/Non-standard_RAID_levels#Linux_MD_RAID_10 > There are also different layouts for raid5 and raid6, though I don't think they make much difference unless you are doing something odd like trying to make your mdadm raid5/6 layout exactly match that of some hardware raid controller. There are also special layouts that are used as intermediary steps in converting between raid5 and raid6 - you won't want to touch these. So raid10 is the only level with /useful/ layout options. The different options can make a measurable speed difference, with the best choice depending on the load. The "far 2" layout is, I think, the best choice for common ready-heavy loads.