Is having only one disk a DBA's choice or is how ODA delivers the disks?

We have a customer whose database disks for ASM, local backup, and the /u01 mount point (for software installation) are all part of a single disk (vdb), which has been partitioned into multiple sections. This setup is in a virtual machine inside a virtualized ODA (through KVM).

I'm not very familiar with ODA and have a question: Is having only one disk a choice made by the DBA who configured the virtual machine, or is this the way ODA provisions disks in a VM (a single large disk)?

In the virtualized environments we typically manage (non-ODA), I usually see multiple disks allocated for ASM rather than just one.