Если кому-то это еще интересно, то
"Microsoft® SQL Server™ 2000 indexes are organized as B-trees. Each page in an index holds a page header followed by index rows. Each index row contains a key value and a pointer to either a lower-level page or a data row. Each page in an index is called an index node. The top node of the B-tree is called the root node. The bottom layer of nodes in the index are called the leaf nodes. The pages in each level of the index are linked together in a doubly-linked list. In a clustered index, the data pages make up the leaf nodes. Any index levels between the root and the leaves are collectively known as intermediate levels.

For a clustered index, sysindexes.root points to the top of the clustered index. SQL Server navigates down the index to find the row corresponding to a clustered index key. To find a range of keys, SQL Server navigates through the index to find the starting key value in the range, and then scans through the data pages using the previous or next pointers. To find the first page in the chain of data pages, SQL Server follows the leftmost pointers from the root node of the index."

чем определяется размер страницы в МS? какие размеры могут быть у страницы?
Размер страницы жестко задан и составляет 8Kb из которых под данные может быть использовано 8060 bytes.

Т.е. у кластеред индекса нет соответствующей таблицы, где хранятся данные, т.е. все данные полностью хранятся в leaf pages. Я правильно понял?
Да, кластерный индекс и есть собственно сама физически упорядоченная таблица + B-дерево

"The pointer from an index row in a nonclustered index to a data row is called a row locator. The structure of the row locator depends on whether the data pages are stored in a heap or are clustered. For a heap, a row locator is a pointer to the row. For a table with a clustered index, the row locator is the clustered index key ."