Hitch a ride through Google's cloud

Your Gmail box lives somewhere in the jumble of servers, cables, and hard drives known as the "cloud" but it often migrates in search of the ideal location.

Google today released an animation that answers the question: what happens when I press send on Gmail? The company created the interactive feature called The Story of Send to highlight the security and relatively low energy footprint of its data centers. The graphics repeat Google's estimate that its data centers use 50 percent less energy than a typical data center and 30 percent of their data center energy is supplied from renewable sources, including wind and solar.

But in an interview, company representatives disclosed that Google has rearchitected its cloud infrastructure in a way that optimizes its computing resources and improves energy efficiency. They declined to say when the switch was made, but indicated this shared-resources architecture has been in place for some time.

Data centers typically have a redundant fail-over system to ensure data and servers are available for customers. Rather than mirror each data center to another location like it, Google has designed a "one to many" failover system, explained Sabrina Farmer, engineering manager of Gmail. That means if there's a failure in one location, the load is distributed to many data centers.

Treating all of its data centers as a common pool of resources also means that an individual Gmail or Google Apps account isn't tied to a specific location. How often a person uses e-mail, mail volume, and location of the user determines the master and back up "slave" account, Farmer said.

Her corporate e-mail is nearby in Silicon Valley but her personal Gmail is actually hosted in Europe because it provides the optimal performance, she said. Engineers track data, such as average response time, and make changes to where customer accounts are stored to improve performance. Over 90 percent of Gmail e-mails are delivered within five seconds and more than 50 percent arrive in less than a second.

It's an efficient use of compute resources because Google doesn't need to have a full standby system in each of its many locations. The architecture also allows Google to fully use its available resources, rather than have thousands of idle servers.

"The fact that we don't have to have spares is a significant cost savings to running the product," she said. "It was a major change in how we manage resources and distribute load."

Representatives declined to attach a figure to efficiency savings but said it was significant and driven by the company's push to improve efficiency and lower its carbon footprint. Farmer said engineering behind the move was significant but the company can now better tweak application performance by moving user accounts among locations.

"We look at users' activity constantly and if we find you will perform better by moving your account, we will," she said.