From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Williams Subject: Re: [mdadm git pull] "--assemble --scan" support for imsm Date: Tue, 17 Aug 2010 09:49:01 -0700 Message-ID: <4C6ABD7D.7050909@intel.com> References: <4C69D525.4060404@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4C69D525.4060404@gmail.com> Sender: linux-raid-owner@vger.kernel.org To: "K. Posern" Cc: "linux-raid@vger.kernel.org" , dave.jiang@intel.com List-Id: linux-raid.ids [ added linux-raid with permission ] On 8/16/2010 5:17 PM, K. Posern wrote: > Dear Mr. Williams, > > I am a bit desperate that's why I dare to contact you like this: > As I did not find any answer to my below 2 questions in man-pages, in > the source-code (quick look with grep+less), on irc channels and of > course with google, I am hoping that you can give me any hint or refer > me to somebody who might. > > I adore Intels engagement for linux. Unfortunately is there no website > (yet?): "intellinuxraid.org" (like there is: intellinuxgraphics.org). There is no website. My personal thought is that we should extend the content at raid.wiki.kernel.org. > The only official information from intel I could dig up so fare states: > imsm is supported with mdadm >=v3 and dmraid >=v1 > > But I am trying to find out if it is possible to: > > a) Autoassemble the RAID (so avoid having an initrd) No, the auto-assemble I mentioned in the pull request will not avoid having an initrd. You are thinking of "in-kernel autodetect" which is not supported with the imsm metadata format (or any metadata format besides the md-v0.90 format). In general assembling arrays in userspace is much more flexible which is why you see the in-kernel autodetect code has been put in a no-new-features/maintenance-only mode. I know Fedora and OpenSUSE have added support for this configuration to their initrd tools. > b) BOOT linux from this: grub2? lilo? ... anything? One of the primary benefits of using the Intel(R) RST (mdadm-imsm) format is that you can use the platform bios option-rom to boot from raid. So grub, grub2, lilo, or any other bootloader can boot from raid. This is because the option-rom installs a bios int13 handler that allows the bootloader to read from a raid volume as if it were a standalone disk. > About (a): > The git pull request seems to indicate thate there is auto-assembly > support for imsm software raids?! > Is this true? - again: grep The "mdadm -As" command will search all available disks and automatically assemble all the imsm arrays that it finds. > What RAID-Levels (for an imsm fakeraid) are supported? I think the 'fakeraid' moniker is tired and misplaced when referring to this new functionality in md/mdadm. There is nothing fake about Linux software RAID. I prefer "bios-raid" or even "software raid". Current platforms ship support for raid levels 0, 1, 10, and 5. > Especially: What about RAID-0? Supported. > > About (b): > According to "Kyron" and his wiki: > http://wiki.neuralbs.com/index.php/Gentoo_Quick_Install_notes#GRUB2 > grub2 should support imsm (but grep for imsm in the Bazaar checkout does > not yield any hit) <<< I contacted the grub2 mailing-list for clarification Like I mentioned above, the bootloader does not need any special code to boot from a bios-raid array because it can use standard int13 services. > I really hope you can help me. Most importantly with question (a). > > > Yours sincerely, > > K. Posern > Regards, Dan