For Oracle Clusterware installations, you must also add additional disk space for the Oracle ASM metadata. You can use the following formula to calculate the disk space requirements (in MB) for OCR and voting files, and the Oracle ASM metadata:
total = [2 * ausize * disks] + [redundancy * (ausize * (all_client_instances + nodes + disks + 32) + (64 * nodes) + clients + 543)]
redundancy = Number of mirrors: external = 1, normal = 2, high = 3, flex = 3.
ausize = Metadata AU size in megabytes
all_client_instance = Sum of all database clients
nodes = Number of nodes in cluster.
clients - Number of database instances for each node.
disks - Number of disks in disk group.
For example, for a four-node Oracle RAC installation, using three disks in a normal redundancy disk group, you require an additional 5293 MB of space: [2 * 4 * 3] + [2 * (4 * (4 * (4 + 1)+ 30)+ (64 * 4)+ 533)] = 5293 MB
