Re: combining two raid systems

[maarten <maarten@ultratux.net>]

On Thursday 13 January 2005 20:17, maarten wrote:
> Hi,
>

Some more info:  The mdadm --detail --scan still cannot find the other md 
devices so I examined the boot.log.  It starts out assembling the right md 
device (the one I want as the first) but it then rejects it.
Sorry, I have to type this in from the console since my booted kernel is not 
the same version as the /lib/modules version on disk (it being the wrong disk 
and all) so I can't load any modules, thus no network connectivity there...

It sees the partitions, but it says a couple of times 
"invalid raid superblock magic on ..."
but then it continues with something like:
created md1
bind <hda3>
bind <hdc3>
bind <hde3>
bind <hdg3>
bind <hdq3>
bind <hds3>
running: <hds3><hdq3><hdg3><hde3><hdc3><hda3>
personality 4 is not loaded !

And then it stops md1again.

This same, or analogue, thing happens thereafter with md0 but now it says 
personality 3 is not loaded !

Now I have to wonder... personality isn't the raid level, is it ? Because I 
would never ever use or need raid-3 or raid-4.  What's happening here ?

And these two arrays, that are attempted at boot at least, won't show up later 
in mdadm --detail --scan.   If I run --examine on one of those partitions it 
clearly sees it being part of an array, but --detail differs in this respect.

I think I may now want to remove the 0xFD flags on all the arrays of system 2 
so as to disable them, but that still might not fix the missing personalities 
problem...
Well first I'll examine the boot.log of the system 1 to see if when booted 
standalone it says things about personality 3 & 4 as well...

Any help greatly appreciated !

Maarten

> I'm currently combing two servers into one, and I'm trying to figure out
> the safest way to do that.
>
> System one had two md arrays: one raid-1 with the OS and a second one with
> data (raid-5)  It is bootable through lilo
>
> System two had 9 arrays, one with the OS (raid-1) two raid-1's for swap,
> and 6 md devices that belong in an LVM volume. This system has grub.
>
> All md arrays are self-booting 0xFD partitions.
>
> I want to boot off system one.  I verified that that boots fine if I
> disconnect all the [system-2] drives, so that's working okay.
>
> Now when I boot I get a lilo prompt, so I know the right disk is booted by
> the BIOS.  When logged in, I see only the md devices from system two, and
> thus the current md0 "/" drive is from system two.  Now what options do I
> have ?
>
> If I zero the superblock(s) (or even the whole partitions) from md0 of
> system 2, it will not boot off of that obviously, but what will now get to
> be md0 ? It could be the second array from system 2 equally well as the
> first array from system one, right ?
>
> I could experiment with finding the right array by using different kernel
> root= commandlines, but only grub gives me that possibility, lilo has no
> boot-time shell (well, it has a commandline...)
>
> Another thing that strikes me is that running 'mdadm --detail --scan' also
> only finds the arrays from system 2. Is that expected since it just reads
> its /etc/mdadm.conf file, or should it disregard that and show all arrays ?
>
> Upon first glance 'fdisk -l' does show all devices fine (there are 10 of
> them)
>
> I think (er, hope, actually) that with mdadm.conf one could probably force
> the machine to recognize the right drives as md0 as opposed to them being
> numbered mdX, but is that a right assumption ?  At the time the kernel md
> code reads / assembles the various 0xFD partitions, the root-partition is
> not mounted (obviously) so reading /etc/mdadm.conf will not be possible.
>
> I'll start to try out some things but I _really_ want to avoid having an
> unbootable system: for one, this system has no CDrom nor floppy, and even
> more importantly I don't think my rescue media have all neccessary drivers
> for the ATA & SATA cards.
>
> Anyone have some good advice for me ?
>
> Maarten

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