From owner-freebsd-questions@freebsd.org Wed Apr 20 00:05:28 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 0D45BB1583C for ; Wed, 20 Apr 2016 00:05:28 +0000 (UTC) (envelope-from xxjack12xx@gmail.com) Received: from mail-io0-x22c.google.com (mail-io0-x22c.google.com [IPv6:2607:f8b0:4001:c06::22c]) (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 DA73A10BD for ; Wed, 20 Apr 2016 00:05:27 +0000 (UTC) (envelope-from xxjack12xx@gmail.com) Received: by mail-io0-x22c.google.com with SMTP id f89so24216509ioi.0 for ; Tue, 19 Apr 2016 17:05:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=v1IoO7oc4T2pY8l5K/uAi3ZLMCxMjfOPNoMDLNfRDyU=; b=wJGPUTEuuob17ErWGg6g2GiCQPduAkgWq/jJlf/dTy1mynpTlhZ+lwtgxB9+vLHBoU GoBrZwRSwIgbHuYYguTyo4uMbGaKoTps+T22he0GrBARVuzwFDqIkzgBE2yRwC5ao3Xd vp1ckJSntFNbLsnG+612RsRSbvpU9OkFZhedVUgNpsQ06FJ8YaIQ/teWnJSbkxILlL8d k8MzFf2Y2jWUTSa6YHafQxuDA3Vh7UsyUUNmVN6DoIt4Zk81VEfoCnfQ+NoVXCbUZRPt mDrXjTfGq1uLLWK8kYVdTUfsisEBKnE0qxEHX5+7Ci5CL61nFA4tCwBRJWsvB0S6MXt8 ZLkg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=v1IoO7oc4T2pY8l5K/uAi3ZLMCxMjfOPNoMDLNfRDyU=; b=NC4vwmRR6IjtlLIkQeNHpOXV+qx1Qja9n0KHaQCUHbkJT/wbZndoyrZe4t2C3jb7Z+ 3xWTzcepqm9rjsHlpjWXX47Dq9T+igpY5m51v+lZHl93q8UsuezdefSnPeDBa5ILDBVZ mcjae4pDDLBA7zY0B7TyFMMJEh/ykKTUfREdUCi+b0tPPR7YEz3B7EUOOUTD0a/8hNxS II+lpRspZXTggw2O6CiQCNTZrdR7m5trpN2t7QEEvYh4MCbZVP7Ncfe0m0ol0B9OyrV9 6JNHOAZv7BbFJf6WKKmgGdoAMbG8o1CX/yL4rLvbEhbjNjQmz5EUV8240AZZgnykBYPd vy4A== X-Gm-Message-State: AOPr4FU5RjfdLG40XCgXJ13/TM7+4VMLBOszV5N4M25yUZoXLD4ZLBWM6wA+fITgfdIYPyFQaoDHeoIy2QN45g== X-Received: by 10.107.59.85 with SMTP id i82mr6743688ioa.134.1461110727317; Tue, 19 Apr 2016 17:05:27 -0700 (PDT) MIME-Version: 1.0 Received: by 10.36.41.129 with HTTP; Tue, 19 Apr 2016 17:04:47 -0700 (PDT) In-Reply-To: <44a8kpcm14.fsf@be-well.ilk.org> References: <571533F4.8040406@bananmonarki.se> <57153E6B.6090200@gmail.com> <20160418210257.GB86917@neutralgood.org> <64031.128.135.52.6.1461017122.squirrel@cosmo.uchicago.edu> <20160419153824.7b679129f82a3cd0b18b9740@sohara.org> <40267.128.135.52.6.1461098148.squirrel@cosmo.uchicago.edu> <44a8kpcm14.fsf@be-well.ilk.org> From: "Jack L." Date: Tue, 19 Apr 2016 17:04:47 -0700 Message-ID: Subject: Re: Raid 1+0 To: "freebsd-questions@freebsd.org" Cc: Valeri Galtsev , "Steve O'Hara-Smith" Content-Type: text/plain; charset=UTF-8 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: Wed, 20 Apr 2016 00:05:28 -0000 On Tue, Apr 19, 2016 at 2:43 PM, Lowell Gilbert wrote: > "Valeri Galtsev" writes: > >> On Tue, April 19, 2016 9:38 am, Steve O'Hara-Smith wrote: >>> On Mon, 18 Apr 2016 17:05:22 -0500 (CDT) >>> "Valeri Galtsev" wrote: >>> >>>> Not correct. First of all, in most of the cases, failure of each of the >>>> drives are independent events >>> >>> If only that were so. When the drives are as near identical as >>> manufacturing can make them and have had very similar histories they >>> can be expected to have very similar wear and be similarly close to >>> failure at all times, which makes it likely that the load imposed by >>> one failing will push another over. >> >> Sigh. You need suggest some physics that will make one drive affect >> another (aged or not aged doesn't matter for me). Then you will have me in >> your team. > > Correlation is not causation. > > It's not a big stretch to imagine that two nearly identical mechanical > devices, operated in nearly identical conditions, might wear out in a > nearly identical way at about the same time. There is no need for one > drive to affect the other. > > A fair number of people believe that this in fact occurs. I've looked > for evidence on the subject, and I haven't found anything (beyond > anecdotes) for or against the possibility. I think all hard drives are garbage and can die at any unpredictable time. Doesn't matter what brand, what model, what type, they all die unexpectedly. With that, I just make sure I have good backups just in case there's multiple drive failures in a raid set.