MegaRAID: All of the disks from your previous configuration are gone

Recently one of my servers has crashed and on reboot I was greeted with the error message below:

FW could not sync up config/prop changes for some of the VD's/PD's.
Press any key to continue, or 'C' to load the configuration utility.

Foreign configuration(s) found on adapter.
Press any key to continue or 'C' to load the configuration utility,
or 'F' to import foreign configuration(s) and continue.

All of the disks from your previous configuration are gone. If this is
an unexpected message, then please power off your system and check your cables
to ensure all disks are present.
Press any key to continue, or 'C' to load the configuration utility.

Entering the configuration utility in this state will result in drive
configuration changes. Press 'Y' to continue loading the configuration utility
or please power off your system and check your cables to ensure all disks are
present and reboot.

All of the disks from your previous configuration are gone.

This was the scariest error message I have encountered in a long time. Did I just lost a terabyte of valuable data even though I was using a redundand RAID configuration? I have of course backed up everything but I still did not want to spend the day rebuilding the system from scratch.

Fortunately, I was able to put back the LSI MegaRAID controller configuration and no data was actually lost.

In case this occurs to someone else, here are the steps that I did to recover my server.

1. Enter the LSI MegaRAID BIOS configuration utility. Press ALT-S, then RETURN.
   
   
   
   
2. You are now in the home screen of the LSI MegaRAID BIOS Config Utility. It should look similar to this screenshot (if not, press ALT-D, then RETURN). Note that all my disks are in the state "Unconfigured Bad" for some reason.
   
   
   
   
3. Press ALT-H, then select the first Unconfigured Bad disk drive by pressing the ARROW-DOWN key, then RETURN.
   
   
   
   
4. You now see some information for the selected physical disk drive. Force the drive in the "Unconfigured Good" state by pressing ALT-U, SPACE, ALT-G, then RETURN.
   
   
   
   
5. The next page is for setting some more disk drive attributes, which we don't need. Go back to the home screen by pressing ALT-B, then RETURN.
   
   
   
   
6. Repeat this until all of your "Unconfigured Bad" drives are in the "Unconfigured Good" state. After that, let the LSI MegaRAID controller re-scan all physical disk drives to read the configuration, which is conveniently stored somewhere on each physical disk drive. Press ALT-S, then RETURN.
   
   
   
   
7. Hopefully, the Scan Devices command has recovered the RAID configuration. In my particular setup I have four physical 500 GByte disk drives that are configured as one single RAID-10 virtual disk drive with 1 TByte capacity. I am not sure how this dialog looks like if there are more than one virtual disk drives configured, if that is the case you need to continue on your own from here on. In case anything goes wrong it is however possible to run the "Scan Devices" command again and try something different.
   
   Anyway, if your configuration is similar to mine press ALT-P, then RETURN.
   
   
   
   
8. If the configuration could be read successfully from the devices, a preview dialog is displayed. The RAID controller has successfully read the configuration which looks in fact exactly how the system was configured earlier. Press ALT-I, then RETURN to import the configuration.
   
   
   
   
9. The LSI MegaRAID Controller has recovered its drive configuration. Everything looks good so far. You can now restart the system: press ALT-X, then RETURN.
   
   
   
   
10. Press ALT-Y, then RETURN
    
    
    
    
11. Finally, physically reset or power-cycle the system. This can't be done from the utility.
    
    

System is back!

After the reboot the RAID controller was in its previous state and the server could be started successfully.