Conceptual view of the bandwidth savings ...
Savings of backing up 92GB over a 155Mbps link with 100 ms latency:
These savings are above and beyond those you already get with using TSM Fastback (taken from solution brief):
The IBM Tivoli Storage Manager FastBack provides an extensive and cost-effective data protection and recovery solution specifically designed to help remote offices maintain operations, regardless of the type of data loss.The FastBack Client uses next-generation, block-level technology to capture new and changed data on the application servers as frequently as needed—up to true CDP—with almost no performance impact on the applications. This provides for much more granular recovery, leaving much less data at risk of loss than traditional once-a-night backup solutions.The FastBack Server provides the management, policy engine, and local repository for the protected data. The server includes near-instant restore capabilities, enabling critical applications to resume within seconds following almost any type of data loss. The server also initiates “selective replication” jobs to send copies of selected data over the WAN to another location for disaster recovery and backup consolidation capabilities.The FastBack DR Server aggregates the backup data from multiple remote offices—enabling extremely fast recovery of remote office workloads should an office go offline for any reason. The FastBack DR Server also can be used to enhance protection of business-critical application servers in the data center, and it integrates easily with central data protection and retention solutions such as IBM’s Tivoli Storage Manager.
TSM Fastback is a solution that has seen strong adoption from customers with remote offices ... If backup times or bandwidth usage over a WAN are a concern, I suggest you look into the WXC offering from Juniper Networks in concert with TSM Fastback.