Using v$filestat one can find the physical reads and writes to datafiles it also includes reads done by RMAN. So using this SQL one can find physical read and write on a filesystem. Note: The data reported is since the database started.

SQL> column filesystem format a40
SQL> SELECT substr(vdf.name, 1, instr(vdf.name, '/', -1)) filesystem, sum(vfs.phyrds) totalreads, sum(vfs.phywrts) totalwrts
FROM v$filestat vfs, v$datafile vdf
WHERE vfs.file# = vdf.file#
GROUP BY substr(vdf.name, 1, instr(vdf.name, '/', -1));

FILESYSTEM TOTALREADS TOTALWRTS
—————————————- ————— —————-
/u01/oradata/TEST/data01/ 33397136 1315151
/u02/oradata/TEST/idx01/ 71951 35720
….

Here is the description of the view V$FILESTAT and V$DATAFILE