Windows Live Hotmail is a gigantic service in all dimensions. Here are some of the highlights:

# Is a worldwide service, delivering localized versions of Hotmail to 59 regional markets, in 36 languages.

# They host well over 1.3 billion inboxes (some users have multiple inboxes)

# Over 350 million people are actively using Hotmail on a monthly basis (source: comScore, August 2009).

# They handle over 3 billion messages a day and filter out over 1 billion spam messages – mail that you never see in your inbox.

# They are growing storage at over 2 petabytes a month (a petabyte is ~1 million gigabytes or ~1000 terabytes).

# They currently have over 155 petabytes of storage deployed (70% of storage is taken up with attachments, typically photos).

# They are the largest SQL Server 2008 deployment in the world (they monitor and manage many thousands of SQL servers).

# All in all they keep four copies of your data on multiple drives and servers to minimize the chance of data loss due to a hardware failure.

# Thousands of servers monitor service health, transactions (for example, sending an e-mail) and system performance for customers all over the world.

# They have a round-the-clock response center team that watches over our global monitoring systems and takes action immediately when there is problem. We have an escalation process that can engage our engineering staff within a few minutes when needed.

This should begin to give you a sense of the size and scope of the engineering that goes into delivering and maintaining the Hotmail service.

Regards

Marc Liron
Microsoft MVP

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