Hi [NAME],   The virtual disk will remain in a degraded state until the rebuilding of the drives is completed.     You can check the rebuilding status from Open Manage within the OS or you can follow the below CLI commands from the guide.   [URL]
We have a Dell MD1420 connected to a Dell R730. This morning, we received an idrac email that one of the disks in a RAID6 virtual disk was bad, We replaced it (1.2tb) at around noon. Green lights. I assumed it would sync back into the RAID6 and fix the "degraded" state, It's now five hours later and the virtual disk still hasn't added the new drive back to the RAID6 configuration. ("Remaining Redundancy =1). Is this just a latency issue due to rather large drives or something else?
Why Won't Dell Virtual Disk Add Newly Replaced Drive to Restore RAID6 
Non-Degraded State