Join 2 drives to 1 continguous drive

$ sudo apt-get update
$ sudo apt-get install mdadm

$ sudo fdisk /dev/xvdb
$ sudo fdisk /dev/xvdc

$ sudo mdadm \
    -C /dev/md0 \
    -l raid0 \
    -n 2 \
    /dev/xvd[b-c]1

$ sudo mkfs.ext3 /dev/md0