SQL> SELECT disk_number, label
  2  FROM V$asm_disk;

DISK_NUMBER    LABEL
-----------    -----
         0    F:
         1    G:
         2    H:
         3    I:
         4    J:
         5    K:
         6    L:
         7    M:
         8    C:

9 rows selected.

SQL> CREATE DISKGROUP mydata NORMAL REDUNDANCY
  2     FAILGROUP mydata01 DISK '\\.\F:','\\.\G:'
  3     FAILGROUP mydata02 DISK '\\.\H:','\\.\I:';

Diskgroup created.

SQL> SELECT group_number, name, total_mb,state, type
  2  FROM V$asm_diskgroup;

GROUP_NUMBER   NAME      TOTAL_MB   STATE        TYPE
------------   ------    --------   -------     ------
          1   MYDATA        4108   MOUNTED     NORMAL