The VMware VMDK driver connects to vCenter, through which it can dynamically access all the data stores visible from the ESX hosts in the managed cluster.
When you create a volume, the VMDK driver creates a VMDK file on demand. The VMDK file creation completes only when the volume is subsequently attached to an instance, because the set of data stores visible to the instance determines where to place the volume.
The running vSphere VM is automatically reconfigured to attach the VMDK file as an extra disk. Once attached, you can log in to the running vSphere VM to rescan and discover this extra disk.
