Average Read and Write Delays

USE master
GO

SELECT
    CAST(db_name(a.database_id) AS VARCHAR) AS 'Database',
    b.physical_name                         AS 'File',
    a.size_on_disk_bytes                    AS 'Size',
    a.io_stall_read_ms / a.num_of_reads     AS 'Avg. Read Delay',
    a.io_stall_write_ms / a.num_of_writes   AS 'Avg. Write Delay'

FROM
    sys.dm_io_virtual_file_stats(NULL, NULL) a

    INNER JOIN sys.master_files b
    ON
        a.database_id = b.database_id
        AND a.file_id = b.file_id

WHERE
    num_of_writes       > 0
    AND num_of_reads    > 0

ORDER BY
    'Database',
    a.io_stall DESC