to Erlend trying to use raiddetect and others

[Gerte Hoogewerf]

On Friday 12 November 2004 18:00, Erlend wrote:
> I'm currently running SuSE 9.0 with proprietory Fasttrak driver (only
> works on 2.4 kernel).  Desperate to upgrade to 2.6 kernel.  I played
> around with raiddetect, and got it into the initrd such that it would
> detect raid partitions at boot, but of course it didn't map anything.
Raiddetect was a proof of concept program made by someone knowing how to 
process metadata of several kinds of Vendor raids. Someone knowing about the 
Device-Mapper implementation could use raiddetect's code to really do 
something interesting with it. Suse included raiddetect into its linux 
distribution most probably not knowing what the program was meant for and now 
you are using something that was never meant for end-user purposes.

Some genius decided create a program based on raiddetect. He used the 
device-mapper to map propriatary vendor raids (like medley and promise) so 
people could use the data on disks belonging to these raids while running 
kernel 2.6. He called his tool: dmraid.

> How was I able to get raiddetect to run from initrd without a patch for
> grub? 
Again you are terribly wrong. 

Neither Grub nor Lilo has any problems with raids as long as the BIOS 
represents this raid as a normal device. It's the way we look at the raid 
from within Linux 2.6 that has changed radically. These changes make it 
harder to INSTALL a bootloader properly.

Lilo for example uses syscalls to obtain geometry information of a 
'disk'/partition. These were present in the kernel 2.4 ATARAID framework, but 
with dmraid (using the device mapper) the kernel isn't capable to answer 
lilo's questions anymore. An unpatched Lilo will fail to install if you 
donnot specify enough information in /etc/lilo.conf

> There has been a lot of talk about the lilo patch; is there a similar
> one for grub, or does it not need one? 
I wrote a patch for lilo to give users a big chance of success to install the 
bootloader while using a very minimal /etc/lilo.conf
I published it to show that an existing device-mapper patch (by Saout) breaks 
things for dmraid users.

Three facts for all users:
* Don't use the word "need", as you don't need my patch.
* Don't use Cristophe Saout's devmapper patch as it will take away any chance 
to install the bootloader
* Grub works without any patches. A change in the next dmraid release will 
make it easier to install grub.

One Tip for Erlend:
* Upgrading from Linux 2.4 to 2.6 needs much files/packages to be updated or 
changed. Dmraid tends to make things even more difficult. Continue with the 
things you are doing if you know what you are doing :) Consider to install an 
up-to-date GNU/Linux on a IDE harddisk and doing yours hacks from within this 
installation.

Whenever I'll have the time I'll try to fix Saout's patch to support dmraid. 
Doing all work my study requires, this can take months.

>
> Thanks,
>
> Erlend
>
>

Best regards,
Gerte