A customer has an IBM System Storage DS8700 at their primary site and an XIV system at their recovery site， which is 9.5 kilometers away. They want to replicate data for disaster recovery backup.  Which factor is a primary consideration when proposing a solution for this customer（）

• A、compatibility of copy functions
• B、difference in capacities in the two systems
• C、cache size discrepancies between the two systems
• D、the necessity of using two storage management products