Operating System Support for Massive Replication
The increasing number of devices used by each user to access data and services and the increasing importance of the data and services available electronically both favor "Access-anywhere" network-delivered services. Unfortunately, making such services highly available is difficult. For example, even though end servers or service hosting sites advertise an availability of "Four nines" (99.99%) or "Five nines" (99.999%), the end-to-end service availability (as perceived by clients) is typically limited to two nines because of poor wide area network availability. Moreover, although network bandwidths are improving quickly, network latencies are much more difficult to improve in wide area networks, which limits performance for access-anywhere services if those services are delivered from a single location.