I’ve been working my way through the list of Videos of the Windows Azure Sessions at PDC09 and have noticed some questions and comments on scaling applications.  Sometimes people are saying one type of scaling when they mean the other or just mean improving scaling in general … probably a mistake I’ve made myself a few times.

Here is a reminder for those of us who may not remember which is which all the time (without having to stop and think about it):

Scaling Out – to add more nodes to a system.  With Windows Azure, this would be adding more instances to a role.

Scaling Up – to add more resources to a single node of the system (say more CPU’s or memory).  With Windows Azure, this would be increasing the size of the role’s VM.  According to Dianne O’Brien’s presentation the VM options currently map to:

• Small = 1 core x 1.6Ghz, 1.75GB memory, 250GB storage
• Medium = 2 cores x 1.6Ghz, 3.5GB memory, 500GB storage
• Large = 4 cores x 1.6Ghz, 7.0GB memory, 1000GB storage
• X-Large = 8 cores X 1.6Ghz, 14GB memory, 2000GB storage

Wikipedia has more detail on Scalability