Re: [PATCH] grub-1.98: support for partitionable array v1.2

[Jimmy . Jazz]

 Le 20/07/2010 18:08, Colin Watson a écrit :
> On Tue, Jul 20, 2010 at 05:56:46PM +0200, Gaëtan Schmidt wrote:
>> I modify grub2 to understand mdadm 1.2 partition array without the
>> need to map either the metadevice or the partitions in the device.map
>> file. Just the physical devices are required.  As the meta devices are
>> added, they will be recognized automatically. Only raid 1 is supported
>> for the moment but it can be extended to other layouts.
> You've sent this *just* after I committed patches to trunk to understand
> mdadm 1.x metadata.  Could you please look at trunk instead of 1.98?
>

It looks like I hurt your feelings. Sorry for that. For the patches I
propose, better late than never :)
Anyway, I appreciate your implication in the grub project.

>> mdadm 1.1 is not fit to be bootable, its superblock overlaps the boot
>> sector 0.
> Only if you RAID entire disk devices; it works fine if you RAID
> partitions.
>

That is the main difference and here the patches i *propose* come in handy.
You don't have to repartition or reinstall grub on the failed disk. Just
add the spare and let's go.
It is more like a fake raid but harder to implement w/o scripts.

>> I don't use mdX and md/X syntaxes. md_dX is more relevant because of
>> the mdadm default 1.x kernel device scheme /dev/md_dX.
> We already discussed this and agreed to use md/*.  The current mdadm(8)
> says:
>
>   From kernel version, 2.6.28 the "non-partitioned array" can actually
>   be partitioned.  So the "md_dNN" names are no longer needed, and
>   partitions such as "/dev/mdNNpXX" are possible.
>
> I prefer the explicit namespacing of md/*, and it makes it easier to
> support named arrays in a clear way.
>

That's just about cosmetic. You don't need to declare md partitions or
whatever at all in device.map.
It's just the way it appears in grub.cfg but the names have to be
different from 0.9 arrays' names.

>> grub-setup.c and grub-probe.c have been heavily altered to understand
>> mdadm 1.2 partitionable array. That means, grub-setup.c does not
>> support embedded core image in the MBR first sectors gap (<64k)
>> anymore.
>>
>> To avoid any confusion, grub-setup should be renamed grub-mdraid-setup
>> or something like that.
> No renames were necessary with the branch recently merged into trunk.
> If you need further work to support partitionable arrays, then let's
> discuss that; I don't think it's desirable to create a forked version of
> grub-setup or grub-probe, though.
>

Sorry you did not read the code here

>> For the try and fix version of the patches, please forget it. It is
>> really messy. I am using git for the development and i was not able to
>> convert the bzr repository to git, so i don't have a valid tree.
>> Anyway, if you are interested in it, please let me know.
> Just use bzr instead. :-)
>

IMHO, that's not the best way to spread a project in the community. But
you know now the reason why I'm using grub tarball and delayed so long
to share the patches. Also they need to be reviewed.

> Regards,
>

Jj