On Dell MD3860 attached storage arrays or NetApp storage arrays, the logs showed the following errors:
"CACHE_BACKUP_DEVICE_FAILED"
"CACHE_BACKUP_DEVICE_INSUFFICIENT_CAPACITY"
A cache backup device in the storage array controller has failed and you will need to replace it. The cache backup device configuration does not match the cache memory configuration resulting in more cache memory capacity than cache backup device capacity.
On rare occasions this error may resolved itself, but if it persists, contact technical support to open a case for a replacement storage array controller.
Once the replacement controller has been received, use this article for instructions on how to replace the controller: Storage controller offline in storage array