[Novalug] Problems with debian software raid install.

[David A. Cafaro]

Actually, no, you can boot from software raid.  Like I said, I've  
done this no problem on RedHat systems before.  The hardware only  
needs to know about the MBR sector of the harddrive (which is outside  
of any partitions including raid partitions), Grub is installed in  
that mbr sector and should be raid aware.  Grub then can boot the  
init image of the raided /boot directory on /dev/md0.  At least that  
is how it is supposed to work.  Again, either Grub in debian is not  
raid aware, or I've got a bios issue (I can't currently play with it  
right now, working on another project).

I appreciate your help and suggestion, but, just so you know, modern  
version of Grub and lilo both support booting directly off of  
software raid systems.  I believe it used to be you couldn't do that,  
but as of RHEL 4 at least I can confirm that you can (currently have  
a server doing this).  What I don't know is when/if Debian has a  
version of grub/lilo that can deal with it.

Thanks,
David


On Oct 8, 2007, at 2:11 PM, Joel Fouse wrote:

> Well, if you're doing softward raid then no, you need to be able to  
> boot BEFORE the system can even figure out the raid volumes.  If / 
> boot is on raid, then the hardware better be able to read the raid  
> volumes all by itself without an OS running.  But it sounds like  
> you're talking software raid, not hardware raid, in which case / 
> boot can't be a part of the raid set.
>
> <Untested Speculation>
> It seems to me you could, however, have /boot as a small partition  
> by itself on both drives, and just manually copy stuff from one to  
> the other to keep it in sync.  That way you'd always be booting off  
> of one but have the other as a fallback in case the first bombed.   
> You'd want to install grub in the MBR of both drives as well that way.
> </Untested Speculation>
>
> - Joel
>
> p.s. It seems to me that these wizard-based installers that happily  
> set up LVM for you should be able to throw a warning flag if they  
> notice you're installing your boot stuff inside a software-based  
> raid set.
>
> On Mon, 2007-10-08 at 13:57 -0400, David A. Cafaro wrote:
>> hi Miguel, Actually it's important that all the important stuff  
>> that's need for boot must be on raid (so that recovery is quick,  
>> and a drive failure doesn't lead to a system that can't run). This  
>> server must be geared for uptime, so all systems need to be on  
>> raid, including swap. I've done this on RedHat machines so I know  
>> it can be done with Linux, just have to figure out if it's a  
>> Debian issue or hardware issue (bios setting or something). Thanks  
>> though, David On Oct 8, 2007, at 1:38 PM, Miguel Gonzalez Castaños  
>> wrote: > Hi, > > It's a long time since I don't configure a  
>> software RAID, but I > remember that the swap and the / (root)  
>> partitions I excluded them > from the RAID. All the important  
>> stuff to boot the machine IMHO > should be outside your RAID. If  
>> you can, I'd suggest to plug a > third hard drive and create  
>> partitions for swap and / (var, usr, > etc, should go also here  
>> IMHO). > > Miguel > > David A. Cafaro escribió: >> Ok, I need some  
>> help. I'm normally a RedHat/CentOS/Fedora person, >> but for this  
>> project I needed to go with Debian. One requirements >> is that  
>> the two 160GB hardrives be setup to provide software >> raid. No  
>> problem the Debian installer seems to handle that no >> problem  
>> and I'm able to setup everything how I would like: >> >> /dev/hda1  
>> 108GB raid1 bootable flag >> /dev/hda2 20GB raid1 >> /dev/hda3  
>> 20GB raid1 >> /dev/hda4 2GB raid1 >> >> /dev/hdc1 108GB raid1  
>> bootable flag >> /dev/hdc2 20GB raid1 >> /dev/hdc3 20GB raid1 >> / 
>> dev/hdc4 2GB raid1 >> >> /dev/md0 108GB / raid1 >> /dev/md1 20GB / 
>> home raid1 >> /dev/md2 20GB /tmp raid1 >> /dev/md3 2GB swap raid1  
>> >> >> (that's roughly how it's setup) >> >> All seems to go well  
>> debian install goes right through and >> installs all the  
>> software, claims grub is installed and reboots. >> At which point  
>> I get a no bootable device found. I think maybe >> grub didn't get  
>> install correctly so I try booting into debian >> rescue. Debian  
>> can't mount the raid, doesn't see it, just the raw >> raid  
>> partitions.  Just for kicks I boot Fedora 6 rescue, it sees >> the  
>> partitions no problem and mounts them all for me to work >> with.  
>> So from Fedora 6 rescue I chroot and reinstall grub, >> reboot,  
>> and still no boot devices. Then I find the following >> article:  
>> >> >> http://valery.bgit.net/blog-en/2006/07/30/debian-installer- 
>> sata- >> and-software-raid/ >> >> And figure I'll give that a  
>> shot.  I step through the whole >> article (converting SATA to  
>> PATA instructions) and no problem, >> reboot and no bootable  
>> devices. At this point I've started trying >> to play with the  
>> bios settings to see if that helps, I'm just >> wondering if there  
>> is a known issue with Debian Grub and booting >> from software  
>> raid devices (which should not be a challenge like >> this). Any  
>> clues? >> >> And this is Debian Etch v 4.0 r1 i3. >> >> Thanks, >>  
>> David >> >> >> David A. Cafaro <dac at cafaro.net> >> Cafaro's  
>> Ramblings: www.cafaro.net >> >> >> >>  
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David A. Cafaro <dac at cafaro.net>
Cafaro's Ramblings:  www.cafaro.net