单选题A UNIX customer has a Symmetrix DMX that has crashed three times in the past six months， causing data loss. The customer is shopping for an enterprise storage solution to provide point-in- time copy functionality without a fixed relationship to its pri

A UNIX customer has a Symmetrix DMX that has crashed three times in the past six months， causing data loss. The customer is shopping for an enterprise storage solution to provide point-in- time copy functionality without a fixed relationship to its primaries.  Which IBM solution best meets this customer’s requirements（）