As a cluster file system, VMFS lets multiple ESXi hosts access the same VMFS datastore concurrently. You can connect up to 128 hosts to a single VMFS datastore.

Sharing a VMFS Datastore Across Hosts
The image shows a single VMFS datastore being accessed by multiple servers.

To ensure that the same virtual machine is not accessed by multiple servers at the same time, VMFS provides on-disk locking.

Sharing the same VMFS volume across multiple hosts offers the following advantages:

You can use VMware Distributed Resource Scheduling (DRS) and VMware High Availability (HA).

You can distribute virtual machines across different physical servers. That means you run a mix of virtual machines on each server so that not all experience high demand in the same area at the same time. If a server fails, you can restart virtual machines on another physical server. In case of a failure, the on-disk lock for each virtual machine is released. For more information about VMware DRS, see the vSphere Resource Management documentation. For information about VMware HA, see the vSphere Availability documentation.

You can use vMotion to migrate running virtual machines from one physical server to another. To support vMotion between ESXi 5 and version 3.x or 4.x hosts, virtual machines must be located on VMFS3 volumes. For information about migrating virtual machines, see the vCenter Server and Host Management documentation.