When deploying a web-role to the Windows Azure cloud, what is the default behavior in terms of load balancing? Are there any?
The reason for my question is, that we have the Traffic Manager where you can specify load balancing, fail over and round robin. However, if I do not enable this, how does Azure work behind the curtain then?
The default recommendation in regards to SLA is always at least two instances; but are these two instances serving requests or only one? Hence, default behavior is fail over?
Thanks in advance for any clarifications regarding this matter as I have been unsuccessful finding it on Google.
The default should be round robin, but it is not always 100% guaranteed.
One thing that is sure, is that it is not failover load balancing. The idea is that all your instances are equally loaded, but it cannot be 100% guaranteed all the time.
UPDATE
Nothing in this world is 100% guaranteed :) Even the SLA for compute instances is 99.95% and not 100%. Traffic manager has nothing to do with multi-instance deployments. Traffic manager only takes place when you have deployments across geographic regions.
I've been using, exploring, tweaking, developing for-, porting to- Windows Azure since it's first public CTP back in 2008. I can't remember where do I get all the information from, but the compute load balancer shall be using round robin or similar algorythm (and defenitelly not failover) to spread the load across your instances. Even more, it is "stickyless" if I may say so. Which means that there is no guarantee a request from one user will hit the same instance in the next call.
Some resources on Windows Azure (older and newer):
http://www.davidchappell.com/writing/white_papers/introducing_windows_azure_v1-chappell.pdf
Also, something worth mentioning is that, with the latest release there is also SLA for single instance roles: http://www.windowsazure.com/en-us/support/legal/sla/
Additionally, we will monitor all of your individual role instances and guarantee that 99.9% of the time we will detect when a role instance’s process is not running and initiate corrective action.