Explanation/Reference:
CD: That data remains compressed not only on disk, but also remains compressed in the Exadata Smart Flash Cache, on Infiniband, in the database server buffer cache, as well as when doing back-ups or log shipping to Data Guard.
E (not B): Use the Write-Back Flash Cache feature to leverage the Exadata Flash hardware and make Exadata Database Machine a faster system for Oracle Database Deployments. Write-through cache mode is slower than write-back cache mode. However, write-back cache mode has a risk of data loss if the Exadata Storage Server loses power or fails.
F: Storage indexes are not stored on disk; they are resident in the memory of the storage cell servers.
Incorrect Answers:
A: Storage indexes are not stored on disk; they are resident in the memory of the storage cell servers.
They are created automatically after the storage cells receive repeated queries-with predicates-for columns. No user intervention is needed to create or maintain storage indexes. And because they are memory-resident structures, they disappear when the storage cells are rebooted.
References: http://www.oracle.com/technetwork/testcontent/o31exadata-354069.html