On cloud services web roles you must create at least 2 instances to get Azure's 99.95% SLA because when they do updates to the servers' OS etc, Azure will need to restart the machines (one at a time). This is well documented and you will be shouted at by the portal when running a one instance web role for doing this.
With Azure websites you don't get such warnings and I cannot find any documentation suggesting 2 instances for the 99.9% SLA. However, I also can't find any documentation saying that you don't need 2 instances for this SLA.
So which is it? Do I need 2 instances for Azure websites' SLA like web roles or is that a thing of the past?
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