Re: [gentoo-user] Problems with Nvidia fake raid array

[Michael Orlitzky <michael@orlitzky.com>]

On 07/18/2011 11:08 PM, Jeff Cranmer wrote:
> 
> 
> Pardon my additional questions before taking the plunge here.  
> 
> So, given that I have three devices, /dev/sda, /dev/sdb and /dev/sdc, if
> I run the command mdadm --assemble --scan, would this find all the
> components and create a /dev/md0 disk without damaging the contents of
> the original RAID array?

If you've got the space and time, a backup can't hurt. Using --scan will
make it check the config file, but right now, there's probably nothing
useful in it. This looks like what you want to do to me:

  If the --scan option is not given, then only devices and identities
  listed on the command line are considered.

  The first device will be the array device, and the remainder will be
  examined when looking for components.

but I'd figure out where that md0 is coming from (below) first.


> The only item in /dev/mapper is th default 'control' entry.  There is
> a /dev/md0 item already listed, but presently when I try to mount it, it
> reports that it is unable to read the superblock.  Would the command
> above fix this?

Depends. Where'd the md0 come from? You probably have something in your
logs or dmesg, unless that device was created manually on your old system.


> Where is the config file mentioned in your e-mail, and do I need to edit
> it first to add the three raid disks?

It's /etc/mdadm.conf. You don't need it to create or use the array, but
you'll want to run mdadm when the machine boots and the config file
tells it what to do. Once the array is working, you can just do,

  mdadm --detail --scan >> /etc/mdadm.conf

to populate it. I guess also check to make sure there's no default crap
in there these days.