From owner-freebsd-hackers@freebsd.org Tue Sep 15 22:52:41 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 D166E9C2580; Tue, 15 Sep 2015 22:52:41 +0000 (UTC) (envelope-from mozolevsky@gmail.com) Received: from mail-wi0-x234.google.com (mail-wi0-x234.google.com [IPv6:2a00:1450:400c:c05::234]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 697A71C14; Tue, 15 Sep 2015 22:52:41 +0000 (UTC) (envelope-from mozolevsky@gmail.com) Received: by wiclk2 with SMTP id lk2so47084109wic.1; Tue, 15 Sep 2015 15:52:39 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to:cc:content-type; bh=J/66igBcl8DIAG5+r6Ta9PFaAASr3njGy3pNBbrHGAI=; b=K79NGAiQZjplY1ijOeVGxTZHtaZ8dIjkyi4NT7F8zXzrgXbivdO9Hn46fJn3L7CrMz J6anaeql7y6b/qz1OsACDvHce/7OP2OQsJuxYfXGmRFrtKlClbP71cZNqTlL3iVr6ODz zMy8Jg7xx4m4rFHkco3TnoSU7veKjJxmOiIy3CRifJzdiUjKx8PDirQKN0X2jx4YF6ZN CKIwCRC4z7OalveNd6Sk+nahyEpVOPHDt+yPz6zv09KVKEu+Q4sARScv0u6j8K8tggzw Gq+3eSynBHwxffxKXTfBIeWwfoEGFKjE0dLp2dEOWqkPNZTd4HfQHtKwSZWftk01Jq+v M9Cg== X-Received: by 10.181.13.166 with SMTP id ez6mr12496273wid.24.1442357559559; Tue, 15 Sep 2015 15:52:39 -0700 (PDT) MIME-Version: 1.0 Sender: mozolevsky@gmail.com Received: by 10.28.55.18 with HTTP; Tue, 15 Sep 2015 15:52:00 -0700 (PDT) In-Reply-To: <8435FBF3-2F8E-4A25-ABEA-B7038AFFE372@netgate.com> References: <41EFCF21-D3B0-4EC4-8EAB-417CA33821FC@netgate.com> <8435FBF3-2F8E-4A25-ABEA-B7038AFFE372@netgate.com> From: Igor Mozolevsky Date: Tue, 15 Sep 2015 23:52:00 +0100 X-Google-Sender-Auth: saJB1cOsq7agNNwBVJMRpV6QVBA Message-ID: Subject: Re: ECC support To: Jim Thompson Cc: Dieter BSD , Hackers freeBSD , freebsd-hardware@freebsd.org Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.20 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: Tue, 15 Sep 2015 22:52:42 -0000 On 15 September 2015 at 23:34, Jim Thompson wrote: > 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.