Why does my RAID-1 or RAID-5 report as DEGRADED
RAID-1 and RAID-5 arrays will occasionally report as DEGRADED on boot. Simply put, a status of DEGRADED means the data on one drive does not perfectly mirror the data on the other drive. The resolution for this is to enter the RAID configuration utility on boot and rebuild the array.
This message may point to a hardware error with one of the hard drives in question. To eliminate hardware error as a possibility, first run a Chkdsk on the drive in question. Second, run a hard drive diagnostic to check to see if any errors indicate a possible drive failure. You can check the downloads page for a hard drive utility made by the manufacturer of your hard drives. If the utility reports a failed drive, the drive should be replaced with an identical model prior to rebuilding the array.
Note however that this message reporting a DEGRADED array may not necessarily mean there is a hardware error present at all. If the Hard drive diagnostic reports all disks as healthy, then the most likely culprit for a DEGRADED array is an improper shutdown. If the system is powered off for any reason other than a normal shutdown, files may not be properly mirrored to the disk and degradation may occur. For instance, if a thunderstorm rolls through and your neighborhood loses power, the system will most likely report the array as DEGRADED on the next reboot. A UPS device is recomended for RAID-1 and RAID-5 systems for this reason.
Likewise, if you use sleep mode or put your system into standby, and the system has trouble returning to Windows forcing you to manually power off and turn it on again, the system will report the array as DEGRADED. Avoid using sleep in this instance until you can investigate and resolve the sleep related issue.