Re: Using mdadm instead of dmraid for BIOS-RAID root volume

[Martin Wilck <mwilck@arcor.de>]

On 10/08/2013 04:19 PM, Brian Candler wrote:
>  > Anyway, I'm not so worried about having broken this machine, as it 
> needed a reinstall anyway, but I do wonder what would have been the 
> correct way to get mdraid instead of dmraid at boot time for this root 
> volume?
> 
> After some more searching, it looks like the udev rules were nobbled to 
> disable this in
> https://bugs.launchpad.net/ubuntu/+source/mdadm/+bug/1030292
> 
> A possible way to re-enable is here:
> https://bugs.launchpad.net/ubuntu/+source/mdadm/+bug/1054948/comments/9
> 
> I'm a bit concerned about the issues around clean shutdown, and hence 
> whether is really production-ready yet.

In general, this works. I have seen it work with CentOS, Fedora, and
various SUSE distributions. It may require some work on Ubuntu's side.

 1 The udev rules for incremental mdadm autoassembly need to be in
place. The upstream rules should be fine. They can normally coexist with
the rules for dmraid.
 2 For shutdown, the distro must take care not to kill mdmon before file
systems are unmounted, and to run mdadm --wait-clean after any write
access to file systems is finished.

Martin