Calculates average stalls per read, per write, and per total input/output for each database file

-- Calculates average stalls per read, per write, and per total input/output
-- for each database file.
SELECT DB_NAME(database_id) AS [Database Name] ,
file_id ,
io_stall_read_ms ,
num_of_reads ,
CAST(io_stall_read_ms / ( 1.0 + num_of_reads ) AS NUMERIC(10, 1))
AS [avg_read_stall_ms] ,
io_stall_write_ms ,
num_of_writes ,
CAST(io_stall_write_ms / ( 1.0 + num_of_writes ) AS NUMERIC(10, 1))
AS [avg_write_stall_ms] ,
io_stall_read_ms + io_stall_write_ms AS [io_stalls] ,
num_of_reads + num_of_writes AS [total_io] ,
CAST(( io_stall_read_ms + io_stall_write_ms ) / ( 1.0 + num_of_reads
+ num_of_writes)
AS NUMERIC(10,1)) AS [avg_io_stall_ms]
FROM sys.dm_io_virtual_file_stats(NULL, NULL)
ORDER BY avg_io_stall_ms DESC ;