ASM Disks Performance metric:
SELECT a.name disk_group_name,
b.path disk_path,
b.reads reads,
b.writes writes,
b.read_errs read_errs,
b.write_errs write_errs,
b.read_time read_time,
b.write_time write_time,
b.bytes_read bytes_read,
b.bytes_written bytes_written
FROM v$asm_diskgroup a
JOIN v$asm_disk b
USING (group_number)
ORDER BY a.name
