Date: Tue, 15 Sep 2015 23:52:00 +0100 From: Igor Mozolevsky <igor@hybrid-lab.co.uk> To: Jim Thompson <jim@netgate.com> Cc: Dieter BSD <dieterbsd@gmail.com>, Hackers freeBSD <freebsd-hackers@freebsd.org>, freebsd-hardware@freebsd.org Subject: Re: ECC support Message-ID: <CADWvR2hkd6GGVyfhtiqyvHORSizJyXMEnK8rh%2BM%2BfSBeSGQWQQ@mail.gmail.com> In-Reply-To: <8435FBF3-2F8E-4A25-ABEA-B7038AFFE372@netgate.com> References: <CAA3ZYrBXZn1WpHWYGJYWJDPsk7iDahCas8RhnHC4w%2Babf4w4hA@mail.gmail.com> <41EFCF21-D3B0-4EC4-8EAB-417CA33821FC@netgate.com> <CADWvR2h4XdYfy3i6zjLqC04uqihNwL9QtTgGN%2BZ8QbAkh9=%2BZA@mail.gmail.com> <8435FBF3-2F8E-4A25-ABEA-B7038AFFE372@netgate.com>
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On 15 September 2015 at 23:34, Jim Thompson <jim@netgate.com> wrote: <snip> > I think you=E2=80=99ll find that the default for =E2=80=98scrub=E2=80=99 = is off on most (perhaps > all) boards. There are reasons, and these relate directly to > =E2=80=9Csignificantly diminish system performance=E2=80=9D, (above), as = well as the > greatly increased RAM sizes in use today. > Perhaps I missed something- what point is it that you're trying to make? I was saying that scrubbing aims to remove errors at the source (cf. "on demand") and prevent multi-bit errors that become detectable but irrecoverable, or worse, undetectable. Get hit by a few of the latter two at "interesting" points and you'd wish that scrubbing were on! And seriously, ECC scrubbing is slow but ZFS (or even hardware RAID) scrubbing is lightning fast??! C'mon are we going for data integrity or speed here?! =E2=80=99Scrub' was popular about a decade ago, when DDR2 RAM was around $1= 00/GB. > DDR3-1600 is about $6/GB today. > Yup- with a much higher density of smaller memory bits! ;-) --=20 Igor M.
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