Date: Wed, 16 Sep 2015 12:34:54 +0100 From: Bob Bishop <rb@gid.co.uk> To: Igor Mozolevsky <igor@hybrid-lab.co.uk> Cc: Konstantin Belousov <kostikbel@gmail.com>, Hackers freeBSD <freebsd-hackers@freebsd.org>, Dieter BSD <dieterbsd@gmail.com>, Andriy Gapon <avg@freebsd.org>, freebsd-hardware@freebsd.org Subject: Re: ECC support Message-ID: <3678FC1E-DDC5-4FB2-B6E9-6FC90D0C988E@gid.co.uk> In-Reply-To: <CADWvR2gBDjKFRW-X6ECJaGG7tSvOgk0rTk38O1qQ0hUWjRBF_A@mail.gmail.com> References: <CAA3ZYrBXZn1WpHWYGJYWJDPsk7iDahCas8RhnHC4w%2Babf4w4hA@mail.gmail.com> <55F88A18.6090504@FreeBSD.org> <20150916035904.GE67105@kib.kiev.ua> <93871ADA-EDA3-481C-9959-1D371AB44479@gid.co.uk> <CADWvR2gBDjKFRW-X6ECJaGG7tSvOgk0rTk38O1qQ0hUWjRBF_A@mail.gmail.com>
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Hi, > On 16 Sep 2015, at 11:48, Igor Mozolevsky <igor@hybrid-lab.co.uk> = wrote: >=20 > On 16 September 2015 at 08:51, Bob Bishop <rb@gid.co.uk> wrote: >=20 > <snip> >=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
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