The sp_sysmon output for each data cache includes information that can help you determine the effectiveness for large I/Os. See Performance and Tuning Series: Monitoring Adaptive Server with sp_sysmon, and Chapter 7, “Controlling Optimization,” in Performance and Tuning Series: Query Processing and Abstract Plans.
“Large I/O usage” reports the number of large I/Os performed and denied and provides summary statistics.
“Large I/O detail” reports the total number of pages that were read into the cache by a large I/O and the number of pages that were actually accessed while they were in the cache.
