Michael,

Make sure that the underlying partitions (sda?, sdb?) of md2
are set to type 0xfd, ie. "Linux raid autodetect".

Regards,
Barry Branch

On Sun, 23 Mar 2008, Michael Hannon wrote:

> Greetings.  We've got an Opteron-based system running SL 5.1.  The
> system has an areca RAID controller that we're using in JBOD mode.
> 
> This isn't a question about RAID, but as background information the
> system is set up to have four software-RAID devices, mounted as follows:
> 
>     /dev/md1                /
>     /dev/md0                /boot
>     /dev/md2                /home
>     /dev/md3                /backup
> 
> md0 and md1 are made up from partitions on two drives connected directly
> to the motherboard.  md2 an md3 are both formed from drives connected to
> the RAID controller.
> 
> Everything seems to work fine, except that the system "forgets" the
> device md2 after a reboot.  I.e., /dev/md2 is simply not in whatever the
> system uses as a database for devices.  
> 
> Note that the system for some reason "remembers" md3, and that md2 and
> md3 are connected to the same controller.
> 
> The workaround that we've used is to remove the reference to /dev/md2
> from /etc/fstab and then after rebooting:
> 
>     a. force the creation of the device md2:
>                cd /dev
>                ./MAKEDEV -xv /dev/md2
> 
>     b. assemble the RAID array:
>                mdadm /dev/md2 --assemble --scan
> 
>     c. mount /dev/md2 "by hand"
> 
> This is straightforward enough, and it could easily be automated, but
> there must be some way to make /dev/md2 permanent.  I don't recall that
> we had to do anything special for /dev/md3 (again, coming from the same
> controller).
> 
> Please let me know if you have some way to fix this.
> 
> Thanks.
> 
> 					- Mike
>