From owner-freebsd-arch@FreeBSD.ORG Wed Aug 25 01:51:57 2010 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 98D6D1065672 for ; Wed, 25 Aug 2010 01:51:57 +0000 (UTC) (envelope-from adrian.chadd@gmail.com) Received: from mail-iw0-f182.google.com (mail-iw0-f182.google.com [209.85.214.182]) by mx1.freebsd.org (Postfix) with ESMTP id 5AD468FC0C for ; Wed, 25 Aug 2010 01:51:57 +0000 (UTC) Received: by iwn36 with SMTP id 36so129257iwn.13 for ; Tue, 24 Aug 2010 18:51:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:received:sender:received :in-reply-to:references:date:x-google-sender-auth:message-id:subject :from:to:cc:content-type:content-transfer-encoding; bh=C+n4G+tYFzPgwdRdiKULxztljynPHHLtwqtkABoTJE0=; b=CNzYt78WBd2wh71Yd+ZyhGucl296kYm+tTmf8xi2Px7Bv+BgX//YFpT7TKxu5wqrLn l7NdOP42aBEIzFIGjZ7uUPLFtPejJjmOuWf7KREXVJlkOIS8tr0fIpDYJ6SIpaCkyjT5 SxvfWE8D83SUfz8d4n6j3DZ3KYKLDZtZkVV7g= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=CBgD1ihveY6Gl1UDq1ZEPeUr2xLNcrZGEScQY1AwuQyhZDdLOwv+sbgl+EQL7CmN8T D1XZepZryO61eL/KXlgvBvulZ14pezY2bj+aW/ezZAOTCo8wr4MxA4vCEw9YIUmMJZpa JVkruvE7hZPFwCStsxJ4Hy0M7H91uEdJZ67XM= MIME-Version: 1.0 Received: by 10.231.148.195 with SMTP id q3mr9239909ibv.199.1282699323033; Tue, 24 Aug 2010 18:22:03 -0700 (PDT) Sender: adrian.chadd@gmail.com Received: by 10.231.168.14 with HTTP; Tue, 24 Aug 2010 18:22:02 -0700 (PDT) In-Reply-To: <20100824.105546.1002438156525560711.imp@bsdimp.com> References: <760A97A4-62D2-4900-915D-CA5D889855E1@mac.com> <20100824155205.C2A535B23@mail.bitblocks.com> <20100824.105546.1002438156525560711.imp@bsdimp.com> Date: Wed, 25 Aug 2010 09:22:02 +0800 X-Google-Sender-Auth: Xmr9owVOhwyj2exg1SO6HNzb-Rg Message-ID: From: Adrian Chadd To: "M. Warner Losh" Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Cc: xcllnt@mac.com, freebsd-arch@freebsd.org Subject: Re: RFC: enhancing the root mount logic X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 25 Aug 2010 01:51:57 -0000 On 25 August 2010 00:55, M. Warner Losh wrote: > > You can get away from a large MD by having a small MD and pivoting to > large storage. =A0Linux does this, as Bakul said, and it scales from the > ultra-small 4MB Mips router up to the highest multicore server. > But as someone's said before - and as I've been a Linux sysadmin here and there, I've been bitten more than once by the linux mdroot setup where only the -bare minimum- modules needed to bring the system up are in the mdroot. Woe be if you have to swap hardware in a hurry - double woe if your distribution provides lots of nice "autodetect" methods for figuring out which modules should be in the mdroot and does this for you automatically. You can manually build modules into mdroot but that isn't any good when you're trying to boot a post-failed system on alternative hardware. The FreeBSD method has been nice - I can compile a lean GENERIC but use /boot/loader.conf to load modules at boot time to use alternative storage/network mechanisms. I'm not saying the whole Linux initrd approach is -bad-; i'm just saying it needs to be thought through a little more first. Adrian