Email is your online Identity, how is Hotmail run?

Email is very important, online you can’t go without it. As Dick Craddock, one of the Hotmail engineering team leads, says: “Email is your online identity.”

Hotmail has lots of users. There’s over a billion inboxes that generate over 2 petabytes of new storage every month with a grand total of hundreds of petabytes in total! Of course when you run such a large service you will run into major issues.

[What’s with the new golden logo?]

How is Hotmail run? Did you know that there are about 100 different services running all the time? These run on tens of thousands of servers in data centers around the world. You can group them in the following classes:

– Manageability services
– Storage services
– Message delivery services
– Anti-abuse, safety and privacy services
– Data synchronization services
– Site maintenance services
– Application services

To build out and manage all of these services Hotmail uses clusters, hundreds of them with dozens added each year.

A cluster is a management unit of computation, storage, and memory caching servers grouped together in a network unit.  Clusters allow building and running the Hotmail operational system in a repeatable and predictable manner at ever-growing scale. The cluster contains everything necessary to manage and run a set of services for a set of users.

More about this (and tips for developing at scale) can be found in the latest article on Inside Windows Live: Hotmail tips the scales