Re: [gentoo-user] Software RAID-1

[Kerin Millar]

On 24/08/2014 14:51, Peter Humphrey wrote:
> Hello list,
>
> For several years I've been running with / on /dev/md5 (0.99 metadata), which
> is built on /dev/sd[ab]5. At each boot I see a message scroll by saying
> something like "No devices found in config file or automatically" and then lvm

LVM does not handle md arrays.

> continues to assemble md5 anyway and mount its file system. The rest of my
> partitions are on /dev/md7 (1.0 metadata), which is built on /dev/sd[ab]7. Oh,
> except for /boot, which is on /dev/sda1 with a copy on /dev/sdb1.
>
> So I decided to clean up /etc/mdadm.conf by adding these lines:
>
> DEVICE /dev/sda* /dev/sdb*
> ARRAY /dev/md5 devices=/dev/sda5,/dev/sdb5
> ARRAY /dev/md7 devices=/dev/sda7,/dev/sdb7
> ARRAY /dev/md9 devices=/dev/sda9,/dev/sdb9
>

Perhaps you should not include /dev/md5 here. As you have made a point 
of building the array containing the root filesystem with 0.99 metadata, 
I would assume that it is being assembled in kernelspace as a result of 
CONFIG_MD_AUTODETECT being enabled. Alternatively, perhaps you are using 
an initramfs.

Either way, by the time the mdraid init.d script executes, the /dev/md5 
array must - by definition - be up and mounted. Does it make a 
difference if you add the following line to the config?

   AUTO +1.x homehost -all

That will prevent it from considering arrays with 0.99 metadata.

On a related note, despite upstream's efforts to make this as awkward as 
possible, it is possible to mimic the kernel's autodetect functionality 
in userspace with a config such as this:

   HOMEHOST <ignore>
   DEVICE partitions
   AUTO +1.x -all

Bear in mind that the mdraid script runs `mdadm --assemble --scan`. 
There is no need to specifically map out the properties of each array. 
This is what the metadata is for.

--Kerin