Explanation
Cascade replication on a Dell Unity XT is a configuration in which a block resource is replicated synchronously from one site to another, in a cascading manner. This means that a block resource is first replicated from site A to site B, then from site B to site C, and so on. This creates a chain of replicated resources that are all in sync with each other. This type of replication is useful in cases where data loss is not acceptable, and a zero RPO is needed. It also allows for creating multiple failover points in case of a disaster, providing a higher level of data protection. It's important to note that this type of replication requires a high-speed and reliable network connection between all the sites, and it requires a higher level of planning and maintenance compared to asynchronous replication.

Explanation
The maximum number of SAS buses per SP for a Dell Unity XT 480F without an additional SAS I/O module is 2. Each Dell Unity XT 480F has 2 Service Processors (SPs) and each SP has 2 SAS buses, for a total of 2 SAS buses per SP. SAS buses are used to connect the storage drives to the SPs and to the storage array. Each bus can support multiple drives and provide high-speed data transfer between the drives and the SPs.