If the array is showing degraded but the drives are fine, then your virtual disk (array) has been corrupted and the only way to "fix" it is to delete the array and reconfigure it. If you want to disable the S100, boot to the BIOS Setup F2, SATA Settings, and change it to AHCI instead of RAID.  This will let you use the drives individually in the OS, however, I don't think you will be able to access the data on the drives after switching - you would need to backup/restore.
I'd like to disable the software raid option on this server and use both drives as storage. Is that possible? The Raid 1 degraded a year ago and Dell support helped me restore the server, but we were unable to correct the degraded condition. It was deduced the errors were raid software since the drives checked out. Ken
Disable Perc S100 on T110 Server