ORA-15410
Disks in disk group string do not have equal size.
Cause
The disks in the disk group are not of equal size.
Action
Ensure that all disks in the disk group are of equal size. If adding new disks to the disk group, their size must be equal to the size of the existing disks in the disk group. If resizing, all disks in the disk group must be resized to the same size. If the size of the new disk being added is higher than the existing disks in the disk group, use the size option to specify the size that matches the existing disks.