In the Web User Interface utility, under the Advanced > Disks section, the Disk Configuration pane shows the installed disks “Hotplug Indicator”. There are three color indicators available for the Hotplug Indicator, Red, Yellow and Green.
The effect of disk removal/failure, and Hotplug Indicator color, varies, depending on the RAID level and whether the RAID is in a normal or degraded state. You can determine the effect of disk removal/failure by looking at the Hotplug Indicator on the Disks page. If this indicator is Green, disk removal/failure has no effect on the RAID. If this indicator is Yellow, disk removal/failure causes RAID degradation, but you still can access all the data. If the indicator is Red, disk removal/failure causes the entire RAID to fail.
For example, in a RAID 5 configuration, all the disks are Yellow. Removing any one of them causes the RAID to be degraded, but all the data is still available. However, after you remove one disk, all the other disks become Red, since removing any one of them at this point causes the entire RAID to fail.
Note: In a linear configuration (RAID 0), the Hotplug Indicators Red for all the disks because removing any one of them removes data from the storage system. However, this does not adversely affect any of the other disks.
In addition, while a disk is being rebuilt, all the other disks are RED, since removing any one of them at this point causes the RAID to fail.