If you are sure that a suitable disk group does not exist on the system, then install or identify appropriate disk devices to add to a new disk group.
Use the following guidelines when identifying appropriate disk devices:
All of the devices in an Oracle ASM disk group should be the same size and have the same performance characteristics.
Do not specify multiple partitions on a single physical disk as a disk group device. Oracle ASM expects each disk group device to be on a separate physical disk.
Although you can specify a logical volume as a device in an Oracle ASM disk group, Oracle does not recommend their use because it adds a layer of complexity that is unnecessary with Oracle ASM. In addition, Oracle RAC requires a cluster logical volume manager in case you decide to use a logical volume with Oracle ASM and Oracle RAC.