 <p>While you can change the VM sizes now as part of an in-place update, you should expect some instance downtime. The Windows Azure fabric controller will walk the upgrade domains, taking 1 upgrade domain down to change the VM sizes, and then moving on to the next. If you have 2 instances, you shouldn't have noticed an entire outage (just 1 machine going down at a time).</p> <p>You can see some further details at <a href="http://msdn.microsoft.com/en-us/library/windowsazure/hh472157.aspx" rel="nofollow">http://msdn.microsoft.com/en-us/library/windowsazure/hh472157.aspx</a>. </p>