Migrating from Linux Mint 17.2 mdadm RAID array to a new one (because I upgraded to larger drives).

1.) Replicate the number of partitions in your new drives.
gdisk /dev/sda
gdisk /dev/sdb

I created 3 partitions of the same same size.
partition #1: +1G (/boot)
partition #2: +60G (swap)
partition #3: rest of it (/)

#note if you are using GPT/gdisk you need to create separate a partition at least 1MB in size (in my case I would a 4th partition and mark it type ef02).

Note again do not make my mistake. You cannot just mark your grub /boot partition as ef02, it will not boot (despite grub2 not complaining during install).

gdisk /dev/sdc GPT fdisk (gdisk) version 0.8.8 Partition table scan: MBR: protective BSD: not present APM: not present GPT: present Found valid GPT with protective MBR; using GPT. Command (? for help): t Partition number (1-3): 1 Current type is 'Linux filesystem' Hex code or GUID (L to show codes, Enter = 8300): ef02 Changed type of partition to 'BIOS boot partition' Command (? for help): wq Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING PARTITIONS!!

2.) Create 3 new mdadm arrays that are suitable:

Note the first mdadm array is my boot so I use RAID 1 and metadata=0.90 (or it will not be able to read/boot)

mdadm --create /dev/md51 --metadata=0.90 --level 1 --raid-devices 2 /dev/sdb1 /dev/sdc1 mdadm --create /dev/md52 --level 10 --layout f2 --raid-devices 2 /dev/sdb2 /dev/sdc2 mdadm --create /dev/md53 --level 10 --layout f2 --raid-devices 2 /dev/sdb3 /dev/sdc3

Note md51=/boot
     md52=swap
     md53=/
3.) Create appropraite filesystems:

mkfs.ext4 /dev/md51 mkswap /dev/md52 mkfs.ext4 /dev/md53
Note md51=/boot
     md52=swap
     md53=/

4.) Mount them and prepare to migrate
I am going to use /mnt/newinstall as the staging ground.

#make staging dir
mkdir -p /mnt/newinstall
#make boot and / inside stage:

#mount them
mount /dev/md53 /mnt/newinstall/ mkdir -p /mnt/newinstall/boot mount /dev/md51 /mnt/newinstall/boot

5.) Migrate with rsync
I am going to omit /media/* and /mnt/* to avoid copying other mounted devices

*If you have ecryptfs you will want to exclude /home/user if mounted so you don't copy both encrypted and decrypted files (doubling your storage usage and also exposing an unencrypted copy of your data).

rsync -Pha --exclude=/proc/* --exclude=/sys/* --exclude=/home/user/* --exclude=/media/* --exclude=/mnt/* / /mnt/newinstall/
#rsync the .ecryptfs info to your user or you will lose access be unable to auto-mount it

rsync -Phaz /home/user/.ecryptfs /mnt/newinstall/home/user

rsync -Phaz /home/user/.Private /mnt/newinstall/home/user

6.) chroot and prepare environment.
mount=/mnt/newinstall for bind in dev sys proc; do mount -o bind /$bind /$mount/$bind done chroot /mnt/newinstall grub-install /dev/sda grub-install /dev/sdb update-grub

#update mdadm
#backup
cp /etc/mdadm/mdadm.conf /etc/mdadm/mdadm.conf-`date +%Y-%m-%d-%s` mdadm --detail --brief --scan > /etc/mdadm/mdadm.conf

#update /etc/fstab /boot, /, and swap, with the right blkid
vi /etc/fstab UUID=1119d26-da8e-4317-a5cb-834402b90501 /               ext4    errors=remount-ro 0       1 UUID=22296bff-79c5-4d19-b343-e21d10c5fe9b TYPE=ext4 /boot           ext4    defaults        0       2 UUID=44423ded-5e6b-4f16-9ca9-b8ef69ce00ed none            swap    sw              0       0

blkid /dev/md51
blkid /dev/md52
blkid /dev/md53

Note md51=/boot
     md52=swap
     md53=/

#update initramfs