Large I/O efficiency

“Large I/O efficiency” estimates the number of useful pages brought in by each large I/O. For example, if the value of “Large I/O efficiency is.5, a 16K I/O returns, on average, 4 2K pages that are needed for the query, and 4 other pages, either empty pages or pages that share the extent due to lack of clustering. Low values are an indication that re-creating the clustered index or running reorg rebuild on the table may improve I/O performance.