Why do I care that VMware ESX uses the VMFS?
VMware’s VMFS was created just for VMware virtualization. VMFS is a high performance cluster file system allowing multiple systems to access the file system at the same time. VMFS is what gives you the necessary foundation to perform VMotion and VMHA. With VMFS you can dynamically increase a volume, support distributed journaling, and the addition of a virtual disk on the fly.
Figure 1: Image Source: VMware.com