Described is data storage system modeling. Received at a first data storage system is information representing a workload for I/O operations directed to a logical devices having storage provisioned on physical devices of a second data storage system. Information representing the workload may be obtained by performing discovery processing to discover performance characteristics of the physical devices of the second data storage system. Discovery processing may include receiving, at the first data storage system, I/O operations from a client directed to the set of one or more logical devices having storage provisioned on the physical devices of the second data storage system. The I/O operations are then issued to the second data storage system. In response, performance data is obtained at the first data storage system representing the workload for the plurality of I/O operations. Performance of the second data storage system is modeled in accordance with the workload.