6.5.1

Table Of Contents
When you run multiple virtual machines, VMFS provides specific locking mechanisms for the virtual
machine files. As a result, the virtual machines can operate safely in a SAN environment where multiple
ESXi hosts share the same VMFS datastore.
In addition to the virtual machines, the VMFS datastores can store other files, such as the virtual machine
templates and ISO images.
Sharing a VMFS Datastore Across Hosts
As a cluster file system, VMFS lets multiple ESXi hosts access the same VMFS datastore concurrently.
Figure 171. Sharing a VMFS Datastore Across Hosts
VMFS volume
host
A
host
B
host
C
virtual
disk
files
VM1 VM2 VM3
disk1
disk2
disk3
For information on the maximum number of hosts that can connect to a single VMFS datastore, see the
Configuration Maximums document.
To ensure that multiple hosts do not access the same virtual machine at the same time, VMFS provides
on-disk locking.
Sharing the VMFS volume across multiple hosts offers several advantages, for example, the following:
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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. If the failure
occurs, 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.
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You can use vMotion to migrate running virtual machines from one physical server to another. For
information about migrating virtual machines, see the vCenter Server and Host Management
documentation.
To create a shared datastore, mount the datastore on those ESXi hosts that require the datastore access.
vSphere Storage
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