You can set the type of SCSI bus sharing for a virtual machine and indicate whether the SCSI bus is shared. Depending on the type of sharing, virtual machines can access the same virtual disk simultaneously if the virtual machines reside on the same ESXi host or on a different host.
SCSI Bus Sharing Options
None
Virtual disks cannot be shared by other virtual machines.Virtual
Virtual disks can be shared by virtual machines on the same ESXi host.Physical
Virtual disks can be shared by virtual machines on any ESXi host.
If you use Windows Failover Cluster, you can use RAW disk and Physical SCSI Bus Sharing option. If you use Oracle RAC on the same ESX host, you can use Virtual SCSI Bus Sharing option.
If you don not use “None” option, you can not use default VMware Snapshot features.
Source : VMware Offical Documents