This is exactly how you'd copy over the partition table for a RAID1 array. In RAID5/6 it doesn't matter as the size of the array is determined by the smallest member.
Originally Posted by darkod
Also, I'd put your swap on a setup raid1 array. In this case, it looks like your swap array didn't sync, or is broken. You could easily stop the array and recreate it. Caution this is off the top of my head, so I could be forgetting a step. Also, you'll want to ensure that md1 is the correct device.
then zero the superblocks
mdadm --stop /dev/md1
Then, recreate the array.
mdadm --zero-superblock /dev/sda5
mdadm --zero-superblock /dev/sdb5
Then make it a swap partition
mdadm --create --verbose /dev/md1 --level=1 --raid-devices=2 /dev/sd[ab]5
Edit your /etc/fstab to mount this array, and update your /etc/mdadm/mdadm.conf file.
Finally, setup your swap to startup on reboot
echo "DEVICE partitions" > /etc/mdadm/mdadm.conf
echo "HOMEHOST fileserver" >> /etc/mdadm/mdadm.conf
echo "MAILADDR email@example.com" >> /etc/mdadm/mdadm.conf
mdadm --detail --scan >> /etc/mdadm/mdadm.conf
update-initramfs -k all -u