From owner-freebsd-questions@freebsd.org Mon Apr 18 22:05:51 2016 Return-Path: Delivered-To: freebsd-questions@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id ED996B13346 for ; Mon, 18 Apr 2016 22:05:51 +0000 (UTC) (envelope-from brandon.wandersee@gmail.com) Received: from mail-io0-f169.google.com (mail-io0-f169.google.com [209.85.223.169]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id C654E1E0F for ; Mon, 18 Apr 2016 22:05:51 +0000 (UTC) (envelope-from brandon.wandersee@gmail.com) Received: by mail-io0-f169.google.com with SMTP id u185so894354iod.3 for ; Mon, 18 Apr 2016 15:05:51 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:references:user-agent:from:to:cc:subject :in-reply-to:date:message-id:mime-version; bh=LuzIaBh/izUkqVoCaLORrHp+hH8uSJ1CBfJFYrmxUwY=; b=d0hkxdD3LWYXeyJCqrYjBAUAtsICB2o4Wv/WZqKOhMIOLx98sjwxGSDa4uK6WlsSdd tBvX3uRaMc17TRbcbXe+roP5X6t3hwu8MT7+WCinNjuW+0+zZpemMgSwXN124ja9QHOr ElOEltsrRonHLMFe4OTvWiDeUUzhQmcGyNlJaDJS8eGRZtrZqG+fY1+FjXYyQTBIcEYY Fpg1VSfLwCLUKr/NNcq9p9wGJQK4P5nrwii4iYTPvTRkO70M1eOZLcKF1ofYJFtmiwKY agKp80+v3XorUy/0UKimjX8O/9I3oxlmWdvgHwDLR4DEmy5kwvVUu+yYrampoI/o3/HJ CWEQ== X-Gm-Message-State: AOPr4FXBWCQlAWkvLeldJwYlV5JHQ8ccgR+b1n+XveFyUAqJ9KC9H3+VFLiaZfpmv3/svA== X-Received: by 10.107.52.12 with SMTP id b12mr175195ioa.6.1461017145146; Mon, 18 Apr 2016 15:05:45 -0700 (PDT) Received: from WorkBox.Home.gmail.com (97-116-17-82.mpls.qwest.net. [97.116.17.82]) by smtp.gmail.com with ESMTPSA id zy9sm504675igc.13.2016.04.18.15.05.43 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 18 Apr 2016 15:05:44 -0700 (PDT) References: <571533F4.8040406@bananmonarki.se> <57153E6B.6090200@gmail.com> <20160418210257.GB86917@neutralgood.org> User-agent: mu4e 0.9.16; emacs 24.5.1 From: Brandon J. Wandersee To: "Kevin P. Neal" Cc: Shamim Shahriar , freebsd-questions@freebsd.org Subject: Re: Raid 1+0 In-reply-to: <20160418210257.GB86917@neutralgood.org> Date: Mon, 18 Apr 2016 17:05:44 -0500 Message-ID: <86k2jupo7b.fsf@WorkBox.Home> MIME-Version: 1.0 Content-Type: text/plain X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 18 Apr 2016 22:05:52 -0000 Kevin P. Neal writes: > On Mon, Apr 18, 2016 at 09:07:07PM +0100, Shamim Shahriar wrote: >> On 18/04/2016 20:22, Bernt Hansson wrote: >> > Hello list >> > >> > >> > Used gstripe to stripe the arrays raid/r0 + r1 into stripe0 >> > >> Hi >> >> I'm sure there are people with more expertise than I am, and they can >> confirm either ways. But in my mind, given that you used RAID1 first >> (mirror) and then used those two RAID1 to create a RAID0, this is >> logically RAID 1+0. In other words, if you lose one disc from each of >> the RAID1 you are still safe. If you lose both from one single mirror >> array (highly unlikely), the stripe is unlikely to be of any use. > > Not that unlikely. If you take identical disks from the same company and > subject them to identical load then the probability that they will fail > around the same time is much higher than random. > > That's why when I set up a mirror I always build it with drives from > different companies. And I make it a three way mirror if I can. Sorry to drag this off-topic, but I've heard this advice more than once now, and have to ask: when you say "same company," do you mean same vendor or same manufacturer? I thought having all disks be of the same make and model was ideal, as it avoids problems arising from the different ways each manufacturer fudges their total disk capacity. If I'm wrong, how so? If you mean buying disks of the same make and model from different vendors is ideal, what's the reasoning there? -- :: Brandon J. Wandersee :: brandon.wandersee@gmail.com :: -------------------------------------------------- :: 'The best design is as little design as possible.' :: --- Dieter Rams ----------------------------------