root on RAID

[Glenn Hudson]

RedHat Linux 6.1 has the following warning:

http://www.redhat.com/support/hardware/intel/61/rh6.1-hcl-i.ld-5.html#ss5.6
5.6 RAID Contr ollers Known Issues:
The installation of Red Hat Linux's root partition onto a RAID device is
not supported.
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Do you know what problems having the root partition on RAID will cause?
 
If root is not on a RAID controller and the disk with the root partition
fails, wont the system stop?