After an improper shutdown or restart:
Systems with a Mac Pro RAID Card or Xserve RAID Card may start up to a blinking question mark, or RAID volumes may not mount. RAID Utility may show the volumes, RAID sets, and disks are all viable or good.
An Xserve configured with an SSD and Mac OS X Server installed on the SSD may start up but the RAID volume(s) configured on the RAID Card may not mount.
These symptoms may occur if the LUN map has been damaged and needs to be re-created.