From owner-freebsd-current@FreeBSD.ORG Wed Nov 7 14:01:46 2007 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 6E1E916A41A for ; Wed, 7 Nov 2007 14:01:46 +0000 (UTC) (envelope-from askbill@conducive.net) Received: from conducive.net (conducive.org [203.194.153.81]) by mx1.freebsd.org (Postfix) with ESMTP id 3858813C4B9 for ; Wed, 7 Nov 2007 14:01:46 +0000 (UTC) (envelope-from askbill@conducive.net) Received: from cm218-253-81-177.hkcable.com.hk ([218.253.81.177]:63305 helo=pb.local) by conducive.net with esmtpsa (TLSv1:AES256-SHA:256) (Exim 4.63 (FreeBSD)) (envelope-from ) id 1IplTE-000Ffl-4i for freebsd-current@freebsd.org; Wed, 07 Nov 2007 14:01:28 +0000 Message-ID: <4731C537.9030101@conducive.net> Date: Wed, 07 Nov 2007 09:01:27 -0500 From: =?UTF-8?B?6Z+T5a625qiZIEJpbGwgSGFja2Vy?= User-Agent: Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.8.1.2) Gecko/20070221 SeaMonkey/1.1.1 MIME-Version: 1.0 To: freebsd-current@freebsd.org References: <487375.1457.qm@web30309.mail.mud.yahoo.com> <9bbcef730711070450x308129b4rb18577c317eee197@mail.gmail.com> <4731B8DA.8010201@conducive.net> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Subject: Re: geom_raid5 inclusion in HEAD? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 07 Nov 2007 14:01:46 -0000 Ivan Voras wrote: > 韓家標 Bill Hacker wrote: >> Ivan Voras wrote: >>> On 07/11/2007, Arne Wörner wrote: > >>>> Maybe gjournal could help, because graid5 honors the BIO_FLUSH, but >>>> that is >>>> untested... >>> Yes, AFAIK this would work. >>> >> A RAID5 is one of the harder ones to do both fast and well in >> software-only. >> >> The better hardware ($$$) controllers have fast hardware XOR engines as >> well as CPU-as-state-machines and battery-backed cache, and THEY have to >> work hard. > > I agree. But regarding the immediate topic of gjournal on graid5: > gjournal has hooks in the UFS code to do full sync before journal switch > (commit), which it then propagates to the devices and issues BIO_FLUSH, > so it can offer both speed and reliability in this particular case. > >> Given decent hardware & any UPS that costs less than the hardware >> controller, these are 'choices' - not really show-stoppers. > > In theory this is correct, in practice still many people don't know the > choices they are implicitly making. > I'm all for having it / improving it. GEOM in general and GMIRROR in particular have been *magic* for us as they are much more safely managed over ssh in the absence of an IPMI, IP KVM, or serial link than even a good hardware RAID controller. But I'd not like to see yet-another iteration of 'a little knowledge..' folk follow geom_raid5 as flavor-of-the-month, then expect coders to yet-again defy gravity when the inevitable bites 'em in the anatomy, either. First we walk. THEN we run.... Bill