[ale] Converting to RAID5 root

[H. A. Story]

This defies my logic of RAIDS.   Is this a software RAID?  A RAID 1 
requires at least 2 drives.  A RAID 5 requires at least 3 drives.  You 
don't appear to have enough.  You would need a total of 5 drives for 
this configuration.  Unless you were doing sometime of magic with 
software RAID.  And that some how doesn't sound like a good idea.

However if I am wrong I was reading something the other day about 
initrd.  This would have to be loaded before attempting to mount the 
root.  I THINK.  It needs to load the drivers for the RAID before the 
kernel can boot.

Chris Woodfield wrote:

>OK, here goes...
>
>I'm converting a standard one-drive debian sid installation to a 3- 
>drive RAID. I current have both the original drive and the three SATA  
>drives installed in the system. I've maid the raid partitions with no  
>issues. I have three RAID partitions:
>
>md0	boot partition, RAID 1
>md1	root, RAID 5
>md2 	LVM volume, RAID 5
>
>What I'm trying to do at the moment is make sure I can boot off of  
>the RAID set with md1 as the root partition. Here's the relevant part  
>of menu.lst on the primary drive:
>
>title           Debian GNU/Linux, kernel 2.6.15.4 RAID
>root            (hd2,0)
>kernel          (hd2,0)/vmlinuz-2.6.15.4 root=/dev/md1 ro
>initrd          (hd2,0)/initrd.img-2.6.15.4
>savedefault
>boot
>
>title           Debian GNU/Linux, kernel 2.6.15.4 RAID (recovery mode)
>root            (hd2,0)
>kernel          (hd2,0)/vmlinuz-2.6.15.4 root=/dev/md1 ro single
>initrd          (hd2,0)/initrd.img-2.6.15.4
>savedefault
>boot
>
>I've already copied all the filesystems over to the relevant RAID  
>partitions. RAID is compiled into the kernel.
>
>By all appearances, GRUB is able to boot the kernel that lives on the  
>md0 volume, but I get a kernel panic at the point where the system  
>attempts to mount /dev/md1 as the root volume. The error reads:
>
>VFS: Cannot open root device "md1" or unknown-block(0,0)
>Please append a correct "root=" option
>Kernel panic - not syncing: VFS: Unable to mount root fs on unknown- 
>block(0,0)
>
>Is there something that needs to be set up prior to this mount  
>operation (a boot arg, for example) such that the kernel knows how to  
>assemble /dev/md1? Is this something that should be in the initrd  
>that make-kpkg creates? Any other ideas?
>
>Thanks,
>
>-Chris
>
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