NEC Express5800/R320a-E4 User Manual page 221

When one hard disk with problem was disconnected, SCSI slot changes the status to
"Warning."
IMPORTANT: The status color of the SCSI slot differs depending on the
connection of mirrored hard disks:
If one of the mirrored disks was removed: Warning
If both of the mirrored disks were removed: Gray
Also, at this time, the redundant status of mirrored disks is changed to "Warning."
[SCSI Slot] → [General]
[Mirror Disk]
Installing and Using Utilities 5-61