From owner-freebsd-arm@freebsd.org Thu Mar 24 12:16:48 2016 Return-Path: Delivered-To: freebsd-arm@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 725F1ADB19F for ; Thu, 24 Mar 2016 12:16:48 +0000 (UTC) (envelope-from paul@gromit.dlib.vt.edu) Received: from gromit.dlib.vt.edu (gromit.dlib.vt.edu [128.173.126.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "gromit.dlib.vt.edu", Issuer "Chumby Certificate Authority" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 1D2B21CD2 for ; Thu, 24 Mar 2016 12:16:47 +0000 (UTC) (envelope-from paul@gromit.dlib.vt.edu) Received: from macbook.chumby.lan (c-71-63-91-41.hsd1.va.comcast.net [71.63.91.41]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by gromit.dlib.vt.edu (Postfix) with ESMTPSA id 45D3A956; Thu, 24 Mar 2016 08:16:46 -0400 (EDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 9.3 \(3124\)) Subject: Re: Effect of partitioning on wear-leveling From: Paul Mather In-Reply-To: Date: Thu, 24 Mar 2016 08:16:45 -0400 Cc: Oliver Psotta , freebsd-arm@freebsd.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <20160321175952.GA83908@www.zefox.net> <1458586884.68920.96.camel@freebsd.org> <20160321221153.GB83908@www.zefox.net> <1458600070.68920.107.camel@freebsd.org> <1973487B-0AA7-468D-A9CC-319FBE2122F0@netgate.com> <20160322033417.GD83908@www.zefox.net> <201603230349.VAA20311@mail.lariat.net> To: Warner Losh X-Mailer: Apple Mail (2.3124) X-BeenThere: freebsd-arm@freebsd.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: "Porting FreeBSD to ARM processors." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 24 Mar 2016 12:16:48 -0000 On Mar 24, 2016, at 12:05 AM, Warner Losh wrote: > When you have a fleet of thousands of ssds, you'll get failures no = matter > the quality... Pertinent to discussion of SSD failures is this article about the topic, = which summarises a FAST 2016 paper on the subject: = http://www.zdnet.com/article/ssd-reliability-in-the-real-world-googles-exp= erience/ Here are the "key conclusions" from the ZDNet article (and I quote): "=E2=80=A2 Ignore Uncorrectable Bit Error Rate (UBER) specs. A = meaningless number. =E2=80=A2 Good news: Raw Bit Error Rate (RBER) increases slower than = expected from wearout and is not correlated with UBER or other failures. =E2=80=A2 High-end SLC drives are no more reliable that MLC drives. =E2=80=A2 Bad news: SSDs fail at a lower rate than disks, but UBER rate = is higher (see below for what this means). =E2=80=A2 SSD age, not usage, affects reliability. =E2=80=A2 Bad blocks in new SSDs are common, and drives with a large = number of bad blocks are much more likely to lose hundreds of other = blocks, most likely due to die or chip failure. =E2=80=A2 30-80 percent of SSDs develop at least one bad block and 2-7 = percent develop at least one bad chip in the first four years of = deployment." Cheers, Paul. >=20 > Warner > On Mar 23, 2016 1:55 AM, "Oliver Psotta" = wrote: >=20 >> Which SSDs failed on you, Warner? There sure are some rotten apples, >> but the Samsung 840 pro, for example, were (are) quite reliable. >>=20 >> -Oliver >>=20 >>> On 23 Mar 2016, at 07:45, Warner Losh wrote: >>>=20 >>> Hope your SSDs are better at reporting things than ours. We've seen = some >>> SSDs >>> just fail even though the previous SMART data said we've used maybe = 20% >> of >>> the >>> drive's write ability.... >>=20 >> _______________________________________________ >> freebsd-arm@freebsd.org mailing list >> https://lists.freebsd.org/mailman/listinfo/freebsd-arm >> To unsubscribe, send any mail to = "freebsd-arm-unsubscribe@freebsd.org" >>=20 > _______________________________________________ > freebsd-arm@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-arm > To unsubscribe, send any mail to "freebsd-arm-unsubscribe@freebsd.org" >=20