The rescue cd has the following 'peculiarities' when a raid has been installed.
1. When it boots it will use a swap space if it exists, /dev/sda5 or if raid /dev/md1.
Otherwise it pinches the first handy device.
swapoff -a will release the drive.
2. If there is a raid system, the rescue disk cannot see /dev/md0 or /dev/md1.

Possible steps.
1. mkdir /data
2. mount -t ext3 /dev/sda1 /data
3. cp /data/etc/mdadm/mdadm.conf /etc/mdadm
4. umount /data
5. mdadm --assemble --scan
3.
'device busy' .....
Sometimes when you try to assemble the raid one of the devices making it up will be busy.
Start the raid (if the system allows you to) and it will inform you that
'only one device active' . As soon as it starts
mdadm --stop /dev/md0
This operation will release the 'busy' device.
If --assemble does not work try
mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda1 /dev/sdb1
4.
If a raid system is already present, sometimes the rescue disk will stop at the 'initramfs' shell.
alt+ctrl+del and try again, eventually it will work.