[luau] bootable raid and the MBR

Fri May 24 20:40:00 PDT 2002

Thanks a lot for the answers, Eric.  On a Friday night this little 
thread does not make very interesting reading.  I am okay with how the 
system boots now, it just seems like a bit of a compromise to have the 
mbr residing on a single IDE drive when I should have it on the 
redundant SCSI RAID array.

One would think that I could just remove the IDE drive and the 
installation would of course presume that the mbr is supposed to be on 
the remaining SCSI RAID drives in the system.  It's just that the 
installation won't start without the IDE drive.  Adaptec, the makers of 
this RAID controller, don't see why there should be a problem.  Tyan, 
the motherboard makers, of course figure it must be a controller issue.  
The fstab was a good suggestion, but I can't adjust the MBR parameters 
there.

I think that I will go back to it a bit later tonight, reset the 
motherboard, and boot with only the array.  I am also going to see if 
another OS will boot with only the raid controller present.  Then I am 
going to sing karaoke to it.  Sometimes you gotta get wicked.

Is it the bios that originally determines which drive to take a slice 
from for the MBR, or is it the first OS one installs?

scott

On Friday, May 24, 2002, at 08:06 PM, Eric Hattemer wrote:

> Ok.  There's a lot of stuff here.  And I read it twice, but I'm still a
> little lost.  One thing to keep in mind is that /etc/fstab mounts 
> different
> directories and such from hard drives it found.  The hard drives are
> hard-coded in there according to where it finds them on the 
> motherboard.  So
> linux is never real happy about you moving drives around onto different
> controllers.  Usually you'd have to use a bootdisk and manually change 
> the
> fstab.  That's probably a big part of your problem.  Second, I assume 
> in the
> HD controller bios setup, this isn't in raid array form or anything, 
> right?
> Its also conceivable, although not likely, that the hard drive 
> controller
> uses something weird like LBA or not LBA or something that makes it read
> things differently than the standard controller.  The MBR is a special
> little chunk of the hard drive that holds boot information.  If grub is 
> in
> the MBR, it should load grub, even if the OS is bad and doesn't support 
> the
> controller.  But here's three things to try.
>
> 1.  Install the OS again while the hard drive is on the raid array.  If 
> it
> loads the drivers, it should be perfectly happy with this.  Probably 
> your
> best option.
>
> 2.  Instead of grub, choose lilo to be your boot loader.  You may want 
> to
> use the LBA32 flag, or something like that that has some function in 
> raid
> arrays.
>
> 3.  boot off the install CD, enter rescue mode, figure out what device 
> your
> raid array is called, check your fstab, check your /etc/grub.conf, and 
> make
> sure it all works out ok.
>
> -Eric Hattemer
> ----- Original Message -----
> From: "R. Scott Belford" <sctinc at flex.com>
> To: <luau at videl.ics.hawaii.edu>
> Sent: Friday, May 24, 2002 6:46 PM
> Subject: [luau] bootable raid and the MBR
>
>
>> I have been getting spanked by something throughout the day that 
>> Adaptec
>> and Tyan tech. support have bounced to each other.  I have built this
>> aforementioned server with 2gb ram on Tyan's Tiger mboard with the MPX
>> chipset for dual athlons.  The drive setup of choice is a raid5 scsi
>> array controlled by Adaptec's 3210s controller.  For testing, moving
>> things around, and for off disk archiving, I have placed an IDE drive 
>> on
>> the secondary controller.
>>
>> Redhat's 7.3 install does a great job of recognizing and loading the
>> drivers for the raid controller.  (7.2 required and expert install and
>> loading the drivers from floppy)  The problem, of sorts, comes up 
>> when I
>> choose where to put GRUB.  The MBR is on the IDE drive.  While I can
>> boot this way, and, being a production server, rebooting ought not come
>> up much, it is disturbing that I can't put the MBR on the drives that
>> have the most reliability.
>>
>> I'm smart, so I think, and I'm smarter than this motherboard, so I
>> think, so I take some action.  I take out the ide drive. (after ALWAYS
>> disconnecting power cables) I reboot, make sure that the ide is gone
>> from bios, adjust my boot order in bios to put the raid controller
>> (which shows up specifically) second in line behind the cd rom, and I
>> reboot.  Bios posts, raid controller posts, cdrom spins up to boot 
>> from,
>> blank screen.  Reboot, Try again.  Reboot, Try again.  Reset bios to
>> defaults, try again, reset bios eeprom or whatever that thing is, try
>> again.  Each time I hear the cdrom spin up, I see the floppy drive 
>> light
>> come on, and it is clear that my bios is searching the order I gave it
>> to boot from.  It just won't boot anything.  Open case, disconnect raid
>> array from controller, reboot, this time after posting, etc., the CD
>> spins up and installation begins.  Damn.  Turn off box, reconnect 
>> array,
>> reboot, cdrom spins up and system stays blank.  Curses.  Turn off,
>> reconnect IDE drive, reboot, CD spins up this time and installation
>> begins.  While in Disk Druid I notice this little slice on the ide 
>> drive
>> before the two partitions I put there earlier.  It is my MBR.  My
>> computer seems to like it.  So does my install CD.  My CD only boots
>> when it is there.  I don't like it as much because it is not where I
>> want it.  I curse the MBR.
>>
>> Adaptec says that it is supposed to boot and there must be something
>> wrong with the mboard.  Tyan says they get this alot and that I need to
>> make sure my controller is BBS or something like that, compliant.  I
>> wrote the acronym down at work, but I am not there.  Apparently the
>> controller is compliant, that's why I can see it specifically in Tyan's
>> bios boot order.  The problem here may not be with either.  The problem
>> may be with scott :-)
>>
>> I have a question after all this, I think.  How can I put the MBR on 
>> the
>> RAID array?  I have never had to "put" and MBR anywhere, but perhaps I
>> must boot from a floppy and format the mbr or something.  I don't think
>> that I can boot with a win98 floppy and run fdisk mbr to do this.  Is
>> there something comically easy that I am missing?  Does any wise soul
>> have a suggestion or some insight into this?  You know, come to think 
>> of
>> it. I did not try to boot with another installation CD.  Surely this
>> couldn't be an issue, could it?
>>
>> I curse the MBR
>>
>> scott
>>
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