Any difference between the configuration in the PERC and the configuration on the hard drives, a message appears on boot up: "Configuration of NVRAM and drives mismatch. Run View/Add configuration option of Configuration Utility. Press any key to run the Configuration Utility."  The RAID array configuration is stored in two places: the non-volatile RAM (NVRAM) on the RAID controller and on the hard disk drive. Because of a power outage or configuration change, the configuration in NVRAM now differs from that on the hard disk drive. Perform the following steps to resolve it.  Note: If at any time you are prompted to initialize the array, do not do so. Initializing destroys all data on the logical drive. During the initializing process, all data bits are changed to zero.  1. Press any key to enter the Configuration Utility.  2. From the Management Menu, select Configure.  3. Select View/Add Configuration.  4. Two options are presented: View Disk Configuration and View NVRAM Configuration. Because the            original configuration is stored on the hard disk drive, select View Disk Configuration.  5. Verify that the correct configuration for the RAID array is now displayed.  6. Press the ESC key. When prompted to save the configuration, select Yes.  7. The configuration is now saved to the NVRAM on the RAID controller and matches the configuration on the hard disk drive. When prompted, press any key to continue.  8. Press ESC until prompted to exit. Click Yes to exit.  9. Press CTRL+ALT+DELETE to restart the computer. The server should now start normally.  One more note:                                                                   If you cannot see a view from NVRAM, view from disks option, trying clearing the configuration. Disconnect and power off the PV220. Reboot to the PERC BIOS, verify you are on the external PERC and clear configuration. Hook up 220, power up and reboot the server, you should now get another mis-match and should view from disks.
I recently experienced a power failure on a Dell PowerVault 775N Server, which has connected to it a PowerVault 220S Storage device. Once power was restored and the Server rebooted, I get a beeping sound and an indication on the server that there is a "Configuration of NVRAM and drives mismatch (normal mismatch)" We suspect that the controller card maybe bad.  Could anyone assist who may have experience a similar type problem before and give some directions with resolving this issue? Is the data still retrievable?  Thanks.   
Dell PowerVault 220S Configuration Mismatch