The computer with Asus motherboard based on ICH8R has worked flawlessly for about 1.5 years. Two 250 GB hard disks were in RAID1 divided into two partitions.
Two weeks ago I heard about a problem (the request to press a key when loading) which don't lead to subsequent problems in the operation.
When the system is starting up, the message "Primary HDD not found. Press F1 to resume" is displayed. Pressing F1 leads to usual system start with the message "New device was found ...". When I started to sort out what happened I found out that RAID controller switched over to IDE mode. Disk Management displayed copies of logical disks (originally there were C:, D:, -- but now E: and F: are added with the same sizes and labels). The freshest file dates on the copies coincided with the date when start up problems arose.
When I switched the controller to RAID, RAID1 appeared immediately with the name specified by me in RAID settings. The state of RAID 1 was shown as "Normal" that meant the controller didn't understand that the disks were not synchronized.
That's why it is important to monitor an array's state and to synchronize disks in a mirror or recalculate parity in a RAID 5 periodically. There are situations when a controller loses an array and an user doesn't note or just ignore it as in "RAID seems to work and the rest doesn't matter". However RAID loses its fault tolerance and instead of RAID 1 we get a single backup copy which will not update anymore.
Actually a good example for one of our RAID Tips here.