I have read many articles about HierarchyID

http://msdn.microsoft.com/en-us/library/bb677290.aspx

In above link I found, hierarchy ID take the size is about 6*logAn bits, where A is the average fan-out. Can anybody give me definition of fan out. Is fan out for current level in which you are adding new node or is it considering all node in hierarchy.

For eg

If "A" has two child "B" and "C". "B" and "C" also has 2 children each "D", "E" and "F", "G" respectively.

what is average fan out of "A". Total there are 7 nodes. A,B,C has 2 child each then average fan out is 6/7 OR just 2 as there is no other node in same hierarchy level of A.

Also please forward me any article which has measure performance of heirarchyID Db Type.

Up to How many node I can stored as child of root node. That is just up to one hierarchical level. I.e. I want to find One root node and X child nodes. What will be the max value of X.