The sorted_data option for create index is used when the data to be sorted is already in order by the index key. This allows create clustered index to skip the copy step while creating a clustered index.
For example, if data that is bulk copied into a table is already in order by the clustered index key, creating an index with the sorted_data option creates the index without performing a sort. If the data does not need to be copied to new pages, the fillfactor is not applied. However, the use of other create index options might still require copying.
For more information, see“Creating an index on sorted data”.