What does the storage system use to preserve cache data in the event of a complete controller failure? (Choose the best answer.)

A.
Cache mirroring

B.
Flash read cache

C.
Pre-fetch caching

D.
Read caching

E.
Write caching

Explanation:
https://library.netapp.com/ecm/ecm_download_file/ECMP1394572 (page 65, first bulleted point on the page)