What is the reason for using mirrored cache in Dell EMC Unity storage systems?

A.
Provide a secondary copy of write data for the same Storage Processor
B.
Provide a secondary copy of read cached data for the peer Storage Processor
C.
Provide the only copy of read data for each Storage Processor
D.
Provide a secondary copy of write cached data for the peer Storage Processor
Explanation:
Reference: https://www.emc.com/collateral/white-papers/h15162-emc-unity-high-availability.pdf