[ 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
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