Re: Initrd and software raid [was: Initrd rocks!]
Brian May <bam@debian.org> wrote:
> I believe the kernel raid1 autodetection only works if raid1 is compiled
> into the kernel.
That is true as explained in:
http://marc.theaimsgroup.com/?l=linux-raid&m=105232695713715&w=2
In short, to get autostart with md compiled as modules, you need to
apply an md patch from Paul Clements (I never tried this patch).
BTW, linux-raid seems not to be archived on mlist.linux.raid any more
since about August 2002 which, uhm, sucks.
> In anycase, initrd images generated from mkinitrd in Debian do not
> autodetect.
Also, perhaps it is interesting to note that the md maintainer, Neil
Brown, seems to prefer manual settings in boot params instead of
autodetection for md arrays. Autodetection was advocated in the SW Raid
howto, which is terribly outdated. I for myself switched from
autodetection to manual setting in my GRUB config files and am happy
with this setup (I hate black magic). Example:
kernel /boot/vmlinuz-2.4.18 [your usual kernel cmdline params] root=/dev/md0 ro raid=noautodetect md=0,/dev/hda5,/dev/hdc1
Note: this starts the root array only; the other arrays are started by a
"mdadm -A -s" from /etc/init.d/mdadm-raid.
> IIRC, There is a parameter to mdadm (--scan?) that could be used for
> this, but when I asked the initrd maintainer I was given a good reason
> why it was not used (sorry; I can't remember what this was now; it might
> simply be that the mdadm code is unreliable, inefficient, or buggy).
I think this is unlikely, since (-s = --scan) is what is used in the
Debian aforementioned init script for mdadm (/etc/init.d/mdadm-raid).
Also, I use it without any problem since several months now, but my
setup is not very exotic.
--
Florent
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