I separated the 2 drives in the RAID 1 array.
1 is the old one /dev/sda and is out of date, while the separated other one /dev/sdc was in another drive and mounted and used with more data (updated).
I wonder how mdadm will handle this:
usb-storage: device scan complete
md: md127 stopped.
md: bind
md: md127: raid array is not clean -- starting background reconstruction
raid1: raid set md127 active with 1 out of 2 m........
mdadm --assemble --scan
mdadm: /dev/md/diaghost05102010:2 has been started with 2 drives.
mdadm: /dev/md/diaghost05102010:1 has been started with 2 drives.
mdadm: /dev/md/diaghost05102010:0 has been started with 2 drives.
-bash-3.1# cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid6] [raid5] [raid4] [multipath]
md125 : active raid1 sda1[0] sdb1[1]
14658185 blocks super 1.2........