From mboxrd@z Thu Jan  1 00:00:00 1970
From: berk walker <berk.walker@verizon.net>
Subject: Re: combining two raid systems
Date: Thu, 13 Jan 2005 18:46:21 -0500
Message-ID: <41E7084D.2040607@verizon.net>
References: <200501132017.16910.maarten@ultratux.net>
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To: maarten <maarten@ultratux.net>
Cc: linux-raid@vger.kernel.org
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Maarten, why not just leave them as they are, and mount the secondary FS 
on the primary FS?
Less drag on the power supply, and fewer eggs in the basket.  If you 
can't see the added array, it might be that, even in this great day of 
standardisation, some boxes write to the disk differently, esp. in the 
1st cyl.
Just a thought -
b-

maarten wrote:

>Hi,
>
>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
>
>  
>