onstat -p shows dskreads, dskwrites greater than pagreads, pagwrites. How come?

We have recently noticed that "onstat -p" at one of our instances returns values for dskreads and dskwrites in excess of pagreads and pagwrites respectively. My understanding of those statistics was as follows : pagreads : Number of pages read from disk pagwrites : Number of pages written to disk dskreads : Number of disk I/O operations required to read pagreads dskwrites : Number of disk I/O operations required to write pagwrites Further, I have been assuming that a single dskread or dskwrite could, at the minimum, work with 1 page (though with Read-Ahead turned on, a single dskread could return multiple pages). So, the question is, what explains this anomaly? Rudy