Date: Tue, 15 Sep 2015 16:01:49 -0700 From: "alex.burlyga.ietf alex.burlyga.ietf" <alex.burlyga.ietf@gmail.com> To: Igor Mozolevsky <igor@hybrid-lab.co.uk> Cc: Jim Thompson <jim@netgate.com>, Hackers freeBSD <freebsd-hackers@freebsd.org>, Dieter BSD <dieterbsd@gmail.com>, freebsd-hardware@freebsd.org Subject: Re: ECC support Message-ID: <CA%2BJhTNTrs8uebH4a4Xb3CK4=Br1cYS=NixZD_mBbN07ddww4HQ@mail.gmail.com> In-Reply-To: <CADWvR2hkd6GGVyfhtiqyvHORSizJyXMEnK8rh%2BM%2BfSBeSGQWQQ@mail.gmail.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> <CADWvR2hkd6GGVyfhtiqyvHORSizJyXMEnK8rh%2BM%2BfSBeSGQWQQ@mail.gmail.com>
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On Tue, Sep 15, 2015 at 3:52 PM, Igor Mozolevsky <igor@hybrid-lab.co.uk> wr= ote: > 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?! If I remember correctly enabling Patrol Scrub guaranties that each address gets hit once per 24 hours. So on 128GB system you are generating maybe 1-2MiB/s of reads. I'd say it's a good trade-off if you bothered to put ECC memory in. > > =E2=80=99Scrub' was popular about a decade ago, when DDR2 RAM was around = $100/GB. >> DDR3-1600 is about $6/GB today. >> > > Yup- with a much higher density of smaller memory bits! ;-) > > -- > Igor M. > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org= "
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