select sum(IoStallMS)/(sum(NumberReads)+sum(NumberWrites)) as AvgIOStall_Total from ::fn_virtualfilestats(-1,-1)

select cast(db_name(dbid) as varchar(30)),IoStallMS/(NumberReads+NumberWrites) as AvgIOStall, * from ::fn_virtualfilestats(-1,-1)
order by numberwrites desc

select cast(db_name(dbid) as varchar(30)),IoStallMS/(NumberReads+NumberWrites) as AvgIOStall, * from ::fn_virtualfilestats(-1,-1)
order by numberreads desc

select cast(db_name(dbid) as varchar(30)),IoStallMS/(NumberReads+NumberWrites) as AvgIOStall, * from ::fn_virtualfilestats(-1,-1)
order by AvgIOStall desc