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

[Volker Armin Hemmann <volkerarmin@googlemail.com>]

On Tuesday 19 July 2011 16:36:20 you wrote:
> On Tuesday 19 July 2011 09:06:05 Michael Orlitzky wrote:
> > 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.
> 
> mdadm? that is for linux software raid.
> 
> He wants to use nvidia fakeraid. He needs dmraid for that.
> 
> Build in the dmraid support.
> emerge device-mapper
> emerge dmraid
> add device-mapper to boot runlevel
> done
> 
> If I remember correctly
> 
> oh yeah - nvidia fakeraid is pretty fragile. You should plan to move away
> from it.

addendum: just saw that mdadm >=3 should be able to handle fake raid.

My bad.

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