[klibc] Re: Exporting which partitions to md-configure

Luca Berra bluca at comedia.it
Tue Feb 7 02:43:11 PST 2006

On Mon, Feb 06, 2006 at 06:47:54PM -0800, H. Peter Anvin wrote:
>Neil Brown wrote:
>Requiring that mdadm.conf describes the actual state of all volumes 
>would be an enormous step in the wrong direction.  Right now, the Linux 
>md system can handle some very oddball hardware changes (such as on 
>hera.kernel.org, when the disks not just completely changed names due to 
>a controller change, but changed from hd* to sd*!)
DEVICE partitions
ARRAY /dev/md0 UUID=xxyy:zzyy:aabb:ccdd

would catch that

>Dynamicity is a good thing, although it needs to be harnessed.
> > kernel parameter md_root_uuid=xxyy:zzyy:aabb:ccdd...
> >    This could be interpreted by an initramfs script to run mdadm
> >    to find and assemble the array with that uuid.  The uuid of
> >    each array is reasonably unique.
I could change mdassemble to allow accepting an uuid on the command line
and assemble a /dev/md0 with the specified uuid (at the moment it only
accepts a configuration file, which i tought was enough for

>This, in fact is *EXACTLY* what we're talking about; it does require 
>autoassemble.  Why do we care about the partition types at all?  The 
>reason is that since the md superblock is at the end, it doesn't get 
>automatically wiped if the partition is used as a raw filesystem, and so 
>it's important that there is a qualifier for it.
I don't like using partition type as a qualifier, there is people who do
not wish to partition their drives, there are systems not supporting
msdos like partitions, heck even m$ is migrating away from those.

In any case if that has to be done it should be done into mdadm, not
in a different scrip that is going to call mdadm (behaviour should be
consistent between mdadm invoked by initramfs and mdadm invoked on a
running system).

If the user wants to reutilize a device that was previously a member of
an md array he/she should use mdadm --zero-superblock to remove the
I see no point in having a system that tries to compensate for users not
following correct procedures. sorry.


Luca Berra -- bluca at comedia.it
        Communication Media & Services S.r.l.
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