From owner-freebsd-hackers@freebsd.org Wed Sep 16 11:35:03 2015 Return-Path: Delivered-To: freebsd-hackers@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 ADDD49CEC71; Wed, 16 Sep 2015 11:35:03 +0000 (UTC) (envelope-from rb@gid.co.uk) Received: from mx0.gid.co.uk (mx0.gid.co.uk [194.32.164.250]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 3D44218E1; Wed, 16 Sep 2015 11:35:02 +0000 (UTC) (envelope-from rb@gid.co.uk) Received: from [194.32.164.24] (80-46-130-69.static.dsl.as9105.com [80.46.130.69]) by mx0.gid.co.uk (8.14.2/8.14.2) with ESMTP id t8GBYxFj012557; Wed, 16 Sep 2015 12:34:59 +0100 (BST) (envelope-from rb@gid.co.uk) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2104\)) Subject: Re: ECC support From: Bob Bishop In-Reply-To: Date: Wed, 16 Sep 2015 12:34:54 +0100 Cc: Konstantin Belousov , Hackers freeBSD , Dieter BSD , Andriy Gapon , freebsd-hardware@freebsd.org Content-Transfer-Encoding: quoted-printable Message-Id: <3678FC1E-DDC5-4FB2-B6E9-6FC90D0C988E@gid.co.uk> References: <55F88A18.6090504@FreeBSD.org> <20150916035904.GE67105@kib.kiev.ua> <93871ADA-EDA3-481C-9959-1D371AB44479@gid.co.uk> To: Igor Mozolevsky X-Mailer: Apple Mail (2.2104) X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 16 Sep 2015 11:35:03 -0000 Hi, > On 16 Sep 2015, at 11:48, Igor Mozolevsky = wrote: >=20 > On 16 September 2015 at 08:51, Bob Bishop wrote: >=20 > >=20 >> - You might think that as memory density increases (ie bit cell size > shrinks), error rates would increase. Apparently this wasn=E2=80=99t = so up to 2009 > at least, see: >>=20 >> http://www.cs.toronto.edu/~bianca/papers/sigmetrics09.pdf >=20 > subsection 5.1: >=20 > "=E2=80=A6 Figure 6 indicates a trend towards worse error behavior > for increased capacities, although this trend is not consis- > tent. [etc] That=E2=80=99s talking about DIMM capacity, not the capacity (density) = of individual chips on which they say (at the end of the same = subsection): "The best we can conclude therefore is that any chip size effect is = unlikely to dominate error rates given that the trends are not = consistent across various other confounders such as age and = manufacturer.=E2=80=9D I=E2=80=99ll admit to talking that point up a bit but it is = counterintuitive. Memory designers have always been scared of cosmic = rays etc but the suspected effects simply have not been noticeable. Most = likely as they shrink features ever smaller, other factors like material = purity dominate. > There are also other environmental factors which would be more = apparent in > "lone-server" configuration vs well maintained and insulated data = centres > with very good power conditioning ;-) Indeed, and that=E2=80=99s a whole other PITA. We went to colo and never = looked back, but low-power options for small servers are getting better. > --=20 > Igor M. > _______________________________________________ > freebsd-hardware@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-hardware > To unsubscribe, send any mail to = "freebsd-hardware-unsubscribe@freebsd.org" -- Bob Bishop rb@gid.co.uk