On Sun, 24 May 2015, Another Sillyname wrote:

I suspect you're correct in that I'll end up with the boot partitions
being in RAID1 and the data in RAID6, however I am seriously
considering having the boot in RAID6 as well...if I can integrate the
mdadm.conf into the initramfs properly I can't see a reason not to do
this?

The initramfs is usually located on the boot partition. A raid1 partition 
with a filesystem can be read by the bootloader even if the bootloader 
doesn't understand to start the raid first. This is not possible with 
raid6.

So /boot is usually raid1.

Had a look at the metadata=0.9 option but reading the info on mdadm
metadata I think I'd prefer to have the metadata at the start of the
drive, also it looks like metadata=1.2 has extra functionality that I
may want to use later.

Look at v1.0 superblock, it has the same functionality but stores the 
superblock at the end.

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se