I see your questions are regarding ViPR Object Service and CAS.
You want to know:
What's different between ViPR Object Service and CAS service?
If the customer needs CAS service,should they buy object or CAS? Or need to buy both? And, is CAS exclusive to Centera support?
ViPR CAS is considered an API on top of the object storage engine.ViPR Object and ECS Appliance use the same object storage engine. ViPR CAS is treated the same as Amazon S3, OpenStack Swift, and EMC Atmos APIs. An application that is written to Centera CAS can also write data to ViPR Object and ECS. It's important to note that ViPR Object/ECS Appliance only support Centera basic compliance features. ViPR CAS does not support Centera Compliance Edition+.
The choice depends on the application you are using and ther APIs you need.