Re: Setting up Fakeraid with mdadm

[Dan Ritter <dsr@randomstring.org>]

On Thu, Mar 24, 2016 at 05:08:06PM +0100, Christoph Pleger wrote:
> Hello,
> 
> >>
> >> Isn't it possible to use mdadm for mirroring disks as a whole, instead
> >> of
> >> single partitions?
> >
> > Yes, but if it's going to be your main boot and root, don't do
> > that.
> 
> How is that done if it is not the boot disc? And why can it not be the
> boot disc, though it could with dmraid?


If it's not the boot disk, you do:

# mdadm --create --level raid1 -n 2 /dev/sda /dev/sdb

or other options that make you happy.

If you do this, you can make a filesystem in your new md device,
or you can try to partition it and then make filesystems. This
approach, in my experience, leads to confused initramfs and grub
configs that take hours to debug. So my advice is: don't do
that.

-dsr-