When we launched our first Subversion-on-Bigtable service in 2006 our goal was to scale to support hundreds of thousands of projects, with the idea that we could continue to improve the service over time. A year ago, however, we realized that we would have to rebuild our Subversion service to make dramatic improvements in performance. So, we did what we had to do: we rebuilt our service from the ground up, focusing on speed and reliability.
We are now happy to announce that we have rolled out our new service to all our Subversion users. As a result, most common Subversion operations are about 3 times faster than they used to be.
One of the features of Subversion's HTTP-based protocol is that anyone can browse repositories through a normal web browser. Many open source projects hosted on Google Code use this feature to host websites for their project or post the latest versions of their software. We didn't anticipate how popular this would be when we designed our first Subversion service, but our new system has special optimizations for browser access. Latency for these pages are much lower and international users will see a dramatic improvement. We also set the appropriate caching headers, which can be manually controlled with the google-cache-control Subversion property.
To improve our reliability, our new service now has a custom replication system based on the Paxos algorithm. Whenever you make a change to your repository, the new data is now copied to several different data centers before our service reports that the commit has succeeded --- so you can code in peace knowing that your data is stored safely in multiple locations.
If you haven’t already, we encourage you to try out our new Subversion service and let us know what you think.