dmraid rm_partitions.patch (Was: [Bug 392510] Re: Dual-boot install using mdadm root fails to boot, Bug#534274: [mdadm] mdadm fails to assemble raid array on boot)

[Giuseppe Iuculano]

Hi,

Tormod Volden ha scritto:
> Luke and danwood76, it seems like you haven't read the original bug
> report correctly. He does not want to use dmraid in Linux, only his
> Windows partition uses dmraid. His problem is that dmraid is

The dmraid-activate script uses the newly introduced -Z flag to instruct the
kernel to remove partition device nodes from array member disk.
This was necessary to avoid race conditions with udev and creating UUID/label
symbolic links either for member disk nodes, or dmraid device-mapper nodes.

When you create a raidset in your bios, a metadata is written to the disk,
For example, if you create a dmraid raid1 array, you creat a raidset of 2
*disks*, not partitions but disks!

BIOS raid is something which works at the disk level, just like hardware raid
usually does.
Then if you create mdraid out of the 2 raw partitions, you create mdraid meta
data to the *partitions*. This is dead wrong, the raw disk partitions should
never be used when the disks are part of a raid set.
As with BIOS raid partitions are at the raidset level, not the partition level.


I'm aware that before the introduction of the -Z flag, this wrong setup worked
(some people are using dmraid only to handle the windows partition), so the
question is if we should support users who have the bad setup or not.

IMHO we have these options:

1) leaving things as they are, and doesn't support people using this setup
2) support this setup (create a conf file possibly handled by a debconf question?)


Luke, what do you think about it?


Cheers,
Giuseppe.

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Dual-boot install using mdadm root fails to boot
https://bugs.launchpad.net/bugs/392510
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