I can verify that if a spare disk fails it will follow all failure processes of an active disk. This will include a solid amber light on the disk externally. The blinking of a disk only enables when you set to be enable it in DSM. See Enable or Disable the Disk Indicator Light on page 284 of the Dell Storage Manager 2016 R3 Administrator’s Guide: [URL]  
Sorry for the disturbance, but does anyone know the list of HDD/SSD events, which will cause the front panel LEDs indicating them?  On a particular SC4020 system I found: - The failure of single HDD in hotspare pool changed nothing in drive cage indicators state (both LEDs remained green), however, the fault was perfectly registered in web-console; - The LED control from web-console works fine, both via pop-up menu or HDD replacement wizard; - The HDD failure in a production pool also did not displayed via HDD cage LEDs. As for me, this behaviour looks strange, because the periodical 'alarm lamp' visual seeking remains the easiest way to briefly check the hardware state in 'machinery room'. Could that be an SCOS issue? [IMAGE]SC Screenshots
Compellent SC4020 front LED logics