Synchronous replication is a system that Google Apps uses to store customer's info in two data centers at once, so that if one data center fails, Google says it nearly instantly transfers data over to the other one that's also been reflecting the actions taken by the customer all along.
On the practical side this means that thanks to the cloud-based storage solution, Google customers won't lose any data in a data center failure. Just as crucially, they are theoretically back up and running straight away -- although the online giant does acknowledge that no backup solution is perfect.
This synchronous replication is applied to the entire Apps suite as well as Gmail (Google Calendar, Google Docs and Google Sites), with the sales angle being enterprise-class back-up for all at a much lower cost than if companies were to provide or contract separately for their own data redundancy systems.
Google, ever keen to push its Apps suite to new corporate clients of all sizes, estimates that this kind of backup could cost up to $500 for 25GB of data from other providers, but says it can bundle it in because it's already running large, fast data centers.