The intel Storage Manager in the control panel can be opened and you can check the status of the RAID volume. In the event you loose a disk, just replace the disk, and then go into the Storage Manager to remove the old disk, and insert the new disk into the array. Then it will re-create the RAID volume.
When I had a failure, the system informed me of the problem. The system still booted up but informed me of a problem with the RAID volume. I replaced the disk and then went into the Storage Manger and re-created the Array. Was failry painless, low down time just time to replace the physical disk.
On my XPS Gen2 the documentation on the system was very minimal (Actually think hardly no documentation with the shipped system). I think Dell has improved the documentation, but I think they still lack in that area.
Should be on your driver disc but may want to down load it from the following link to get the most current.