Which feature on the IBM Storwize V7000 will help this customer with the capacity issue at the lowest overall cost?

A customer is running a large Oracle database on its EMC storage and approaching 80% capacity. The customer is budget-constrained and must maintain its legacy storage system for an additional year. The customer has budgeted for an IBM V7000 controller with a limited amount of new disk drives.

Which feature on the IBM Storwize V7000 will help this customer with the capacity issue at the lowest overall cost?
A . Easy tier
B . FlashCopy
C . Metro Mirror
D . Real-time Compression

Answer: D