From owner-freebsd-stable@FreeBSD.ORG Sun Apr 3 17:20:36 2011 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id ECBCB1065674 for ; Sun, 3 Apr 2011 17:20:36 +0000 (UTC) (envelope-from bruce@cran.org.uk) Received: from muon.cran.org.uk (muon.cran.org.uk [IPv6:2a01:348:0:15:5d59:5c40:0:1]) by mx1.freebsd.org (Postfix) with ESMTP id 4C2C18FC08 for ; Sun, 3 Apr 2011 17:20:36 +0000 (UTC) Received: from muon.cran.org.uk (localhost [127.0.0.1]) by muon.cran.org.uk (Postfix) with ESMTP id 6EE08E8136; Sun, 3 Apr 2011 18:20:35 +0100 (BST) DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=cran.org.uk; h=message-id :date:from:mime-version:to:cc:subject:references:in-reply-to :content-type; s=mail; bh=4eir9yxKq8jP0enD2c7gjsDmCBo=; b=cvygrI O71Nnrxq92d3np+eE+Xp7cUSCt1XOmJYmOykaBmk56SN8/dv93QHbIBrlRZ6c1yc y00nC9+BiG8XQQX39a69ZHsU2EMN2GA6VlMGMCMst+an96SZBNepRGt3NT9n3KVr B2CNFUAxq3vGILMbitKFFqxOBUile/Rh1NqUM= DomainKey-Signature: a=rsa-sha1; c=nofws; d=cran.org.uk; h=message-id :date:from:mime-version:to:cc:subject:references:in-reply-to :content-type; q=dns; s=mail; b=c0gQDs66BzboEZGBDnfu/l1fkeqb2nM8 wftVUfM+IDQ3z7Mm4inWdvyssTThYijlVi4+9TWG80Bxvl2thw2sFEp9Rrx4gDuM esgnol2JN6cFoxbLPJudYYc1aw8rycM4aDb86UBU/T8RgO/PaGfarqJoO66Q9CxZ nPzeNxbcBzU= Received: from [192.168.1.69] (188-222-18-231.zone13.bethere.co.uk [188.222.18.231]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (No client certificate requested) by muon.cran.org.uk (Postfix) with ESMTPSA id 378F0E7B60; Sun, 3 Apr 2011 18:20:35 +0100 (BST) Message-ID: <4D98AC5B.1050606@cran.org.uk> Date: Sun, 03 Apr 2011 18:20:27 +0100 From: Bruce Cran User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; en-GB; rv:1.9.2.15) Gecko/20110303 Thunderbird/3.1.9 MIME-Version: 1.0 To: Matthew Dillon References: <87d3l6p5xv.fsf@cosmos.claresco.hr> <874o6ip0ak.fsf@cosmos.claresco.hr> <7b15d37d28f8ddac9eb81e4390231c96.HRCIM@webmail.1command.com> <14c23d4bf5b47a7790cff65e70c66151.HRCIM@webmail.1command.com> <201104020335.p323Zp8Q018666@apollo.backplane.com> In-Reply-To: <201104020335.p323Zp8Q018666@apollo.backplane.com> Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha1; boundary="------------ms080506010204030007090301" X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: freebsd-stable@freebsd.org Subject: Re: Constant rebooting after power loss X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 03 Apr 2011 17:20:37 -0000 This is a cryptographically signed message in MIME format. --------------ms080506010204030007090301 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable On 02/04/2011 04:35, Matthew Dillon wrote: > First, a power loss to the drive will cause the drive's dirty writ= e cache > to be lost, that data will not make it to disk. Nor do you really= want > to turn of write caching on the physical drive. Well, you CAN tur= n it > off, but if you do performance will become so bad that there's no = point. > So turning off the write caching is really a non-starter. Do you know if that's changed at all with NCQ on modern SATA drives?=20 I've seen people commenting that using tags recovers most, if not all,=20 of the performance lost by disabling the write cache. --=20 Bruce Cran --------------ms080506010204030007090301--