[plug] grub query in mixed sata / pata setup

[Denis Brown]

At 11:02 AM 2/08/2007, Tomasz Grzegurzko wrote:
>On 8/2/07, Denis Brown <dsbrown at cyllene.uwa.edu.au> wrote:
> > Hello PLUG list members,
> >
> > Not totally sure if this is sata / pata related but here goes...
> >
> > ASUS P5K mobo with sata controller within the Intel P35 chipset

<snip>

>I'm assuming you're trying to run/boot from grub which resides on a RAID 5.

Thanks, Tomasz.

Sorry poor explanation on my part... no, the data drives (three, /dev/sda, 
sdb, sdc) *will be* in software RAID5 but the *system* drive will simply be 
/dev/sdd as a single device.   There will only be data on the RAID, no 
system files, no boot stuff.

But you have reminded me that once the drives are software-RAIDed all bets 
may be off because at boot time, the system will expect to be at /dev/sdd 
and then it sets up the software RAID (/dev/md0 or somesuch?) at which time 
maybe /devsdd no longer is valid.   <scream!>

>It's a partitioning/filesystem problem. GRUB doesn't understand RAID5,
>only ext2, fat, reiser, and RAID1. I had to set up a system a while
>ago and ended up partitioning a RAID1 for /boot formatted as ext2.
>Google for grub + raid and you'll see what I mean.

Interesting about the formats, thanks.   This (system drive) is formatted 
ext3 which should be understood by Grub at least based on previous Debian 
install experience.   It may be worth my while anyway, forcing it to 
ext2.   IIRC that can be done with a command that removes the extra journal 
data.

>Otherwise, the problem is in the root (hd0,0) or whatever clause. You
>may need to modify this as the BIOS assumes that the root device is
>nearly always hd0,0 but this is not always deterministic.

Hmmm... yes.    As I say the BIOS must be getting something correct as it 
does indeed boot to Grub.   From what I can recall of the boot process the 
BIOS points to the MBR of what it has been told is the first bootable 
drive, then the loader (lilo, grub, ...) takes over.   It seems that I am 
getting as far as Grub anyhow.

As per reply to BillK, I'll have a fresh attack on it tomorrow and will 
feed back any info to the list :-)

Denis