From owner-freebsd-questions@FreeBSD.ORG Fri Aug 22 13:12:54 2014 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id D7E52910 for ; Fri, 22 Aug 2014 13:12:54 +0000 (UTC) Received: from mail-qa0-f52.google.com (mail-qa0-f52.google.com [209.85.216.52]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 8DE713EE9 for ; Fri, 22 Aug 2014 13:12:54 +0000 (UTC) Received: by mail-qa0-f52.google.com with SMTP id j15so9492583qaq.39 for ; Fri, 22 Aug 2014 06:12:47 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:subject:mime-version:content-type:from :in-reply-to:date:cc:content-transfer-encoding:message-id:references :to; bh=YBTxKhdXyMy1RKn+/BB1Qv3L5c2eGWppLyel4WY9Pvg=; b=dU8/hceka6G2I+vZ535x6TuaOW+IaamESGMAz8MIPYRg7bRmHevI3i/maK2ft99u2N u57aXk2Bpe4EGG2f7lngkJ4mMwuzVmH+LC3XDfP+yIAT/+cxzd4bbD3qa9dCdbU2Y0WY kMQOWGMUzoDbzpFp6Nh+T6Lu6p3wRaQmnxDbYc+ur208A3NJKoqxCUyJios7LRbztjb1 GTVGtocC+PKjqKN/XXgW8mekIQpwQggqEDkBSlKTBqQge5gycclvSCv+PJ6HXKUMk9MW tN7eKF+hgs5RKSLeO9EhS4HsY+qqsG+62yzd2csUquLaLREFZ6Ddmw4YUuUJBmQAoeK7 R4Ng== X-Gm-Message-State: ALoCoQnr2gFkAWMjS1HX1fs9NypnoQsosPhv33rw5VSMokGjDaYFTFrWWftBH1hnPqt9O9SqLE1v X-Received: by 10.140.103.75 with SMTP id x69mr7118314qge.17.1408713167026; Fri, 22 Aug 2014 06:12:47 -0700 (PDT) Received: from [192.168.2.65] ([96.236.21.80]) by mx.google.com with ESMTPSA id s13sm34639258qga.40.2014.08.22.06.12.45 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Fri, 22 Aug 2014 06:12:45 -0700 (PDT) Subject: Re: gvinum raid5 vs. ZFS raidz Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) Content-Type: text/plain; charset=windows-1252 From: Paul Kraus In-Reply-To: <201408220940.s7M9e6pZ008296@sdf.org> Date: Fri, 22 Aug 2014 09:12:45 -0400 Content-Transfer-Encoding: quoted-printable Message-Id: <7971D6CA-AEE3-447D-8D09-8AC0B9CC6DBE@kraus-haus.org> References: <201408020621.s726LsiA024208@sdf.org> <53DCDBE8.8060704@qeng-ho.org> <201408060556.s765uKJA026937@sdf.org> <53E1FF5F.1050500@qeng-ho.org> <201408070831.s778VhJc015365@sdf.org> <201408070936.s779akMv017524@sdf.org> <201408071106.s77B6JCI005742@sdf.org> <5B99AAB4-C8CB-45A9-A6F0-1F8B08221917@kraus-haus.org> <201408220940.s7M9e6pZ008296@sdf.org> To: Scott Bennett X-Mailer: Apple Mail (2.1878.6) Cc: Trond.Endrestol@fagskolen.gjovik.no, freebsd-questions@freebsd.org, freebsd@qeng-ho.org X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 22 Aug 2014 13:12:54 -0000 On Aug 22, 2014, at 5:40, Scott Bennett wrote: > Paul Kraus wrote: >> Take a look at the manufacturer data sheets for this drives. All of = the ones that I have looked at over the past ten years have included the = ?uncorrectable error rate? and it is generally 1 in 10e-14 for ?consumer = grade drives? and 1 in 1e-15 for ?enterprise grade drives?. That right = there shows the order of magnitude difference in this error rate between = consumer and enterprise drives. >=20 > I'll assume you meant the reciprocals of those ratios or possibly = even > 1/10 of the reciprocals. ;-) Uhhh, yeah, my bad. > What I'm seeing here is ~2 KB of errors out > of ~1.1TB, which is an error rate (in bytes, not bits) of ~1.82e+09, = and the > majority of the erroneous bytes I looked at had multibit errors. I = consider > that to be a huge change in the actual device error rates, specs be = damned. That seems like a very high error rate. Is the drive reporting those = errors or are they getting past the drive=92s error correction and = showing up as checksum errors in ZFS ? A drive that is throwing that = many errors is clearly defective or dying. > While I was out of town, I came across a trade magazine article = that > said that as the areal density of bits approaches the theoretical = limit for > the recording technology currently in production, the error rate = climbs ever > more steeply, and that the drives larger than 1 TB are now making that = effect > easily demonstrable. :-( It took perpendicular recording to make >1TB drives possible at all.=20 > The article went on to describe superficially a new > recording technology due to appear on the mass market in 2015 that = will allow > much higher bit densities, while drastically improving the error rate = (at > least until densities eventually close in on that technology's limit). = So > it may turn out that next year consumers will begin to move past the = hump in > error rates and will find that hardware RAID will have become = acceptably safe > once again. The description of the new recording technology looked = like a > really spiffed up version of the magneto-optical disks of the 1990s. = In the > meantime, though, the current crops of large-capacity disks apparently > require software solutions like ZFS to preserve data integrity. I do not know the root cause of the uncorrectable errors, but they seem = to vary with product line and not capacity. Whether that means the = Enterprise drives with the order of magnitude better uncorrectable error = rate has better coatings on the platters or better heads or better = electronics or better QC I do not know. So I don=92t know how mud this = new technology will effect those errors. -- Paul Kraus paul@kraus-haus.org