boot time assembly of raid arrays

[Rick Stevens]

On Wed, 2005-10-19 at 13:10 -0400, Mark J Strawcutter wrote:
> rhel4
> 
> I've tried using combinations of md= and raid=noautodetect kernel parameters
> along with settings in /etc/mdadm.conf in an attempt to influence what devices/partitions
> get assembled into md3 at boot time.
> 
> So far, no luck.
> 
> md3 is root.  The correct level-1 array should be sda3 and sdc3.  However, sdd3
> has raid superblock left on it from previous use with preferred minor=3
> 
> It appears that something starts looking at the last/highest disk's partitions and works
> down.  It builds md3 from sdd3 then rejects sdc3 and sda3 as not matching.
> 
> Tried device and uuid options in md= and mdadm.conf but it doesn't help.
> 
> Is there something else that influences how raid arrays are assembled at boot time?

A normal SCSI scan starts from device 7 (or 15 on wide SCSI) and works
its way down in Linux.

Have you tried adding a line such as:

	ARRAY /dev/md3 devices=/dev/sda3,/dev/sdc3 uuid=whatever

to your mdadm.conf file?

How about destroying the RAID superblock on /dev/sdd3 via
 
	mdadm --zero-superblock --force /dev/sdd3

and then mdadm can't do anything with it even if it wanted to (well,
unless you tell it to do a legacy MD array, then all bets are off).
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- Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
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-    They say when you play a Microsoft CD backwards, you'll hear    -
-   Satanic messages, but if you play it forwards, it will install   -
-           Windows...which means Satan is in your system.           -
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