How does Windows Azure perform load balancing?

Question

Hey folks,

I was trying to read up on load balancing in Windows Azure, and all the information about it is extremely vague and non-specific. All I really want is a simple answer: how does Azure perform load balancing?

Many applications use sessions or in-memory data to increase performance. With Azure, I'm not sure if this is possible, because (from what I can tell), Azure doesn't have any sort of "sticky" sessions. Even if it wasn't session-based, but simply IP-based balancing, that would be enough for many applications.

So, the question of the day - how exactly does Azure perform its load balancing?

Answer 1

I think you might be looking for Windows Azure AppFabric and Velocity, specifically. Take a look at one of the PDC sessions for more info.

Answer 2

Simple answer - Azure does not perform any load-balancing, yet. It merely provides you with the capabilities to implement scalable solutions yourself.

Later on Microsoft teams might add pre-configured IP balancer VMs, but at the moment it is up to the developer to either use web farms (with out-of-proc session state), CDNs or something more interesting like a distributed apps (where the processing load is messaged out to multiple worker roles, that are manually balanced via the management API).

Answer 3

Azure handles load-balancing for table storage and SQL Azure by distributing traffic across the instances you set up.

For things like session state with a traditional asp.net app, the session data would be stored in table storage, which would then be available to all your webrole instances. This is mentioned here.