On Monday July 29, mjt@tls.msk.ru wrote:
> martin@hack.org wrote:
> >
> []
> > following some hints i've seen elsewhere on the list i tried to pass md
> > parameters to the kernel ->
> >
> > Booting on Nautilus using machine vector Nautilus from SRM
> > Command line: ro root=/dev/md1 md=1,/dev/sdb5,/dev/sdc2,/dev/sdd2 raid=noautodetect
> > md: Will configure md1 (super-block) from /dev/sdb5,/dev/sdc2,/dev/sdd2, below.
> >
> > with the raid=noautodetect option it works.
> >
> > what other raid/md options can be passed this way? and how do i configure
> > more than one device? geez, hope there's not a 256 char limit to the
> > command line...
>
> You may use md=N,dev1,dev2,... option as many times as you want, i.e.
>
> linux root=... md,1=/dev/sda1,.. md=2,/dev/sda2,...
>
> I think that it's sufficient to tell it about only ONE member of
> an array this way if your raid device has persistent superblock
> (kernel will read superblock from first disk (or second for that
> matter - if you choose to tell it about second disk) and read
> other devices from there).
Nope. You have to list all component devices. (Storing device
identification in the superblock is a bad idea that doesn't work in
general, but does in enough specific cases that people still seem to
like it).
>
> About other options - there are only two, raid= (e.g. noautodetect)
> and md= (above) that are raid-related.
>
> > are these options documented somewhere??
>
> I personally looked at sources in drivers/md/ directory and got the
> above line by reading initialization functions. Maybe it's documented
> somewhere in Documentation/... ;)
Documentation/md.txt
Personally, I am not a big fan of autodetection at all.
I see two reasonable ways to start up the RAID array that
stores the root filesystem.
1/ kernel parameters like:
md=0,/dev/sda1,/dev/sdb1
2/ use an initrd filesystem and a user-mode program that
finds and assembles arrays based on a simple config file.
All non-root raid arrays should be assembled after boot by
a user-mode program.
I use and recommend mdadm
http://www.cse.unsw.edu.au/~neilb/source/mdadm/
You can tell it how to recongnise parts of an array and
it goes hunting, finds them, and assembles the array.
NeilBrown
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