This counter measures the number of physical write I/Os performed against the page file, as opposed to the raw count of pages written out. Because writes can be batched, a low ratio of write I/Os to pages written indicates efficient page-file I/O, while a high ratio suggests the disk is being hit with many small, inefficient writes. For example, if 800 pages were written but only 100 I/Os were issued, the system clustered roughly 8 pages per write, a far more efficient pattern than one I/O per page.