The Linux block layer makes some assumptions about when writes are actually committed to disk. LSI RAID controller logical drives pretend to be SCSI disks, but the firmware and driver doesn't report whether the controller is in "write-through" mode or "write-back" mode. Without this information, the block layer assumes "write-through". This is safe, because the controller has a battery-backed cache.
LSI's engineers know that their driver should handle this better so you don't see this message. But it's not an error, and it doesn't affect the system.
Matt_Domsch |
Linux on Dell systems FAQ-O-Matic : 
What does PERC stand for?