have a look at your /etc/fstab
you might have a setup like this:
/dev/sda1 /boot ext3
/dev/sda2 / ext3
/dev/md0 /mydatamountpoint ext3
/dev/md0 is your RAID-device.
Where does is come from?
What are your RAID-devices (physical members)?
# mdadm --misc --detail /dev/md0
Should tell you.
# mdadm --manage --help
Usage: mdadm arraydevice options component devices...
This usage is for managing the component devices within an array.
The --manage option is not needed and is assumed if the first argument
is a device name or a management option.
The first device listed will be taken to be an md array device, and
subsequent devices are (potential) components of that array.
Options that are valid with management mode are:
--add -a : hotadd subsequent devices to the array
--remove -r : remove subsequent devices, which must not be active
--fail -f : mark subsequent devices as faulty
--set-faulty : same as --fail
--run -R : start a partially built array
--stop -S : deactivate array, releasing all resources
--readonly -o : mark array as readonly
--readwrite -w : mark array as readwrite
This should help you to do some more steps.
- Do a backup of your files
- umount /dev/md0
- mdadm --manage --stop /dev/md0
- now you can access your identical partitions / files and do what you want
- check your /etc/mdadm.conf or similar and check for unneeded entries