From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with archive (Exim 4.43) id 1POHPQ-0007U6-5h for mharc-grub-devel@gnu.org; Thu, 02 Dec 2010 17:13:48 -0500 Received: from [140.186.70.92] (port=59140 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1POHPN-0007Tq-Nu for grub-devel@gnu.org; Thu, 02 Dec 2010 17:13:46 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1POHPM-0007QH-LM for grub-devel@gnu.org; Thu, 02 Dec 2010 17:13:45 -0500 Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.120]:47673) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1POHPM-0007Pl-II for grub-devel@gnu.org; Thu, 02 Dec 2010 17:13:44 -0500 Authentication-Results: cdptpa-omtalb.mail.rr.com smtp.user=psusi@cfl.rr.com; auth=pass (PLAIN) X-Authority-Analysis: v=1.1 cv=3jtQBdTzPyV+fq4oCU/u8ZPrJJGN11HvhaDVxyWhycI= c=1 sm=0 a=8nJEP1OIZ-IA:10 a=pg4Dpxby4z7sZisWVyJ9NA==:17 a=7ZHz_BifY10Xz2tx0XEA:9 a=qJh5_avNlD5zZxC6Unjr8rIMpMIA:4 a=wPNLvfGTeEIA:10 a=pg4Dpxby4z7sZisWVyJ9NA==:117 X-Cloudmark-Score: 0 X-Originating-IP: 72.242.190.170 Received: from [72.242.190.170] ([72.242.190.170:1280] helo=[10.1.1.235]) by cdptpa-oedge02.mail.rr.com (envelope-from ) (ecelerity 2.2.3.46 r()) with ESMTPA id 69/FF-02631-31A18FC4; Thu, 02 Dec 2010 22:13:40 +0000 Message-ID: <4CF81A16.2010606@cfl.rr.com> Date: Thu, 02 Dec 2010 17:13:42 -0500 From: Phillip Susi User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2.12) Gecko/20101027 Thunderbird/3.1.6 MIME-Version: 1.0 To: Neil Brown References: <4CF55680.5010703@cfl.rr.com> <20101201092508.7023f974@notabene.brown> In-Reply-To: <20101201092508.7023f974@notabene.brown> X-Enigmail-Version: 1.1.1 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. Cc: linux-raid@vger.kernel.org, The development of GNU GRUB , John Sheu Subject: Re: Software RAID and Fakeraid X-BeenThere: grub-devel@gnu.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: The development of GNU GRUB List-Id: The development of GNU GRUB List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 02 Dec 2010 22:13:46 -0000 On 11/30/2010 5:25 PM, Neil Brown wrote: > My feeling is that grub just needs to be a bit more careful. > > If the members of the md array are partitions, then installing itself in the > boot blocks of the devices holding those partitions always makes sense. > > If the members of the md array are whole devices, then installing grub in > those devices might make sense depending on specific details of the > metadata. The default should be that it doesn't make sense, but specific > cases do. > e.g. if the metadata (/sys/block/mdX/md/metadata_version) is 0.90 or 1.0, and > the array is RAID1, then grub should install itself in the *array*, not in > the devices. I don't think that is quite right. For software raid, you can't actually install to the array per se, since the bios does not know about it; it only knows about the individual disks. Therefore, grub needs to be installed to the individual disk(s), and preferably on each member of a raid 1 so you can still boot with a failed disk. To do this, it needs the embed area to place the core image into, which doesn't exist if the array uses the whole disk instead of a partition in it. In the case of fakeraid, the bios does know about it, so grub can and does install itself into the array, but since this won't work with true mdadm soft raid using the raw disks, grub needs to be able to tell the difference. Only seeing the members of the array are raw disks instead of partitions is not enough information.