Oracle ASM disks are the storage devices that are provisioned to Oracle ASM disk groups. Examples of Oracle ASM disks include:
A disk or partition from a storage array
An entire disk or the partitions of a disk
Logical volumes
Network-attached files (NFS)
When you add a disk to a disk group, you can assign an Oracle ASM disk name or Oracle ASM assigns the Oracle ASM disk name automatically. This name is different from the path name used by the operating system. In a cluster, a disk may be assigned different operating system device names on different nodes, but the disk has the same Oracle ASM disk name on all of the nodes. In a cluster, an Oracle ASM disk must be accessible from all of the instances that share the disk group.
Oracle ASM spreads the files proportionally across all of the disks in the disk group. This allocation pattern maintains every disk at the same capacity level and ensures that all of the disks in a disk group have the same I/O load. Because Oracle ASM load balances among all of the disks in a disk group, different Oracle ASM disks should not share the same physical drive.