From owner-svn-src-head@FreeBSD.ORG Thu Apr 7 22:02:24 2011 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 4EC9A106566B; Thu, 7 Apr 2011 22:02:24 +0000 (UTC) (envelope-from yanegomi@gmail.com) Received: from mail-pv0-f182.google.com (mail-pv0-f182.google.com [74.125.83.182]) by mx1.freebsd.org (Postfix) with ESMTP id 054068FC0C; Thu, 7 Apr 2011 22:02:23 +0000 (UTC) Received: by pvg11 with SMTP id 11so1327354pvg.13 for ; Thu, 07 Apr 2011 15:02:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type :content-transfer-encoding; bh=N/1P5bMxprBM8FMJ/Kblqtnm7mAutmEfOd5q2pqyJkw=; b=lK2IRedSRpwBK4vaYJqyRplHrfZkEaMBY/vZLfGvBa2MvrUc+KBakct4DdU0Bwwse+ RI463p4+J+2Ra3kXac/cE43WQhBRTR8VF5rsRheme+39n/R4QADOWJ9UKcHfej7csEHy YeHaqYGlh8rX9Z5Wjxow5ZxanVuPWFA18iy5w= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=IO0tOH7ODrx4GwkpjugNGyZE3yVLlCbKFIJbtjcJChc3CbVlbZyv3HNT2lJPXN4OdT /wcb0lDzWNJcugIZxZnedLCYJ103QuVuTt9JjSDASncim/lAtTpXg9l/1leU3E1tyH6V a0oiE4LyV9cxvFS9vOcTkKPrIav64nV+pEblU= MIME-Version: 1.0 Received: by 10.142.237.20 with SMTP id k20mr1103098wfh.170.1302213743216; Thu, 07 Apr 2011 15:02:23 -0700 (PDT) Received: by 10.68.42.3 with HTTP; Thu, 7 Apr 2011 15:02:23 -0700 (PDT) In-Reply-To: <17BA8DDF-54C9-4E1A-B7DC-A8935B42EC3E@bsdimp.com> References: <201104070817.p378HrHc033571@svn.freebsd.org> <20110407190318.GA97508@freebsd.org> <17BA8DDF-54C9-4E1A-B7DC-A8935B42EC3E@bsdimp.com> Date: Thu, 7 Apr 2011 15:02:23 -0700 Message-ID: From: Garrett Cooper To: Warner Losh Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: svn-src-head@freebsd.org, Alexander Best , Alexander Motin , src-committers@freebsd.org, svn-src-all@freebsd.org Subject: Re: svn commit: r220412 - in head: share/man/man4 sys/cam/ata X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 07 Apr 2011 22:02:24 -0000 On Thu, Apr 7, 2011 at 2:23 PM, Warner Losh wrote: > > On Apr 7, 2011, at 3:00 PM, Garrett Cooper wrote: > >> On Thu, Apr 7, 2011 at 12:03 PM, Alexander Best wr= ote: >>> On Thu Apr =A07 11, Alexander Motin wrote: >>>> Author: mav >>>> Date: Thu Apr =A07 08:17:53 2011 >>>> New Revision: 220412 >>>> URL: http://svn.freebsd.org/changeset/base/220412 >>>> >>>> Log: >>>> =A0 Make ada(4) driver to control device write cache, same as ata(4) d= oes. >>>> =A0 Add kern.cam.ada.write_cache sysctl/tunable to control it alike hw= .ata.wc. >>> >>> how hard would it be to support per device sysctls/tunables? i'd really= like to >>> do: >>> >>> kern.cam.ada.0.write_cache=3D0 (root fs) >>> kern.cam.ada.1.write_cache=3D1 (/usr, /var, etc.) >> >> Does it really make sense to turn on write caching for one drive and >> not the other(s)? > > Think about /usr/obj or /tmp and ask that question again. =A0Or any files= ystem that's mounted that you don't really care about the contents of acros= s a power cycle. =A0If you have to recreate it, that's OK. =A0 In those cas= es, you may want the speed increase over safety that write_cache gives you.= =A0Or maybe you have a drive that's doing write caching correctly and one = that doesn't. Alex, Warner: thanks for the practical example; I hadn't really considered that :). Cheers! -Garrett