Through Below Script you are able to identify the I/O utilization By per databases in your SQL Server.The information returned by DMV is the data that SQL Server has been recorded since the last restart and therefore it is cumulative data:-
WITH IO_Uses_Per_DB
AS
(SELECT
DB_NAME(database_id) AS Database_Name
, CONVERT(DECIMAL(12,2), SUM(num_of_bytes_read + num_of_bytes_written) / 1024 / 1024) AS Use_Total_Mb
FROM sys.dm_io_virtual_file_stats(NULL, NULL) dmivfs
GROUP BY database_id)
SELECT
Database_Name
,Use_Total_Mb
,CAST(Use_Total_Mb / SUM(Use_Total_Mb) OVER() * 100 AS DECIMAL(5,2)) AS [I/O_Uses%]
FROM IO_Uses_Per_DB
ORDER BY [I/O_Uses%] DESC;