The second major characteristic is network deduplication or caching. When implemented correctly, this feature set can have an enormous impact on the effectiveness of your WAN bandwidth -- sometimes appearing to magnify it many times over. Essentially, network deduplication functions between a minimum of two WAN acceleration devices: one at the head end site and one at the remote site. When data (a file, for example) is requested from the head end site and sent to the remote site, the head-end accelerator makes a note of what that traffic flow looked like. At the same time, the accelerator at the remote site caches that data on its own disk.
The next time that same file (or a file with significantly identical portions) is requested again, the data is thawed out of the cache on the remote-side WAN accelerator and sent directly to the client without being resent over the WAN. This can massively accelerate lots of different types of traffic, including file-sharing data, e-mail data, and SAN-to-SAN replication.
Combined with the single-hierarchy presentation available in Microsoft's DFS, implementation of a caching WAN accelerator can be an extremely effective solution for WAN bandwidth creep. Though the best of these devices can be quite expensive, when weighed against the recurring WAN bandwidth costs, they are usually a very good investment and well worth investigation.
The bottom line for distributed data
No silver bullet can solve all the challenges of managing storage in a distributed enterprise network. Yet storage centralization, server-based computing, and WAN acceleration all offer good options that can improve the efficiency of your storage hardware investments -- and slash your recurring WAN bandwidth costs.