Synchronous replication at Google datacenters

In a blog post today, Google essentially reminds its enterprise customers that Google Apps provides an alternative to expensive, complex solutions as far as data disaster recovery goes.

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.
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.