Hi Phil,

Ok, so your create operation will be:

mdadm --create /dev/md1 --level=10 -n 6 --layout=f2 --chunk=64
--data-offset=variable /dev/sdd1:2048 /dev/sdg1:4096 /dev/sdf1:2048
/dev/sdb1:2048 /dev/sdc1:2048 /dev/sde1:2048

No --assume-clean?

I'm actually guessing that /dev/sdb1 and /dev/sdc1 need offset 2048 like
the original devices, not the 4096 of a device added later (newer
mdadm).  With the mixed offsets, you need mdadm version 3.3.

I created and used it this with mdadm 3.2.5, do I really need to get 3.3?

Use "fsck -n" to verify the array before mounting anything, just in case
one or both of those drives really does need :4096.

Great!