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Doubts about virtual CPUs and Swift storage capacity.


Hi, I would like to understand two things important here in this moment. 

1) What really means a virtual CPU? How does Openstack/KVM deal with CPU allocation from host to instances? For example: I have a compute node, with 2 six cores Xeon, totalizing 24 threads. If I instantiate 24 instances, is it guaranteed that each one will use one thread of CPU or isn't possible to determine how the scheduling will occur? I'm asking that because the applications I will run have intense CPU use. I think I would get better performance if I ensure that instances doesn't shared threads. Is that true? Each instance with one dedicated thread.

2) About Swift, how do I determine the total usable storage capacity of the system? For example: I have 3 nodes with 5 HDs of 1 TB each one. Straightly I have 15 TB of space. If I use raid 1 I can say that I'm going to have 7,5 TB of usable space. And with Swift, is it possible to determine this usable space? 


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