Setting the multi-writer flag on a VMDK

Clustered applications often need to be configured in such a way where multiple servers perform read/write operations to the same volume.  One such example is Oracle RAC.

With VMware virtual machines, VMDK multi-writer sharing is turned off by default.  However, it can be turned on without much trouble.

As the use case is quite specific, you’ll probably be doing this on the creation of the VM/disk.

Let’s take a look at how to do this on ESXi 6.5u1:

From the vSphere web client…  begin provisioning the VM as you normally would.  When you reach ‘Customize Settings,’  toggle the value to multi-writer in the Sharing section. Then, click click next to proceed with setup.

NOTE: the volume must be Thick provisioned, eagerly zeroed to enable this feature.


When configuring the 2nd member of the cluster, you’ll simply add an existing hard disk (the multi-writer volume specified above).

If you were to view the .vmx of one of the VM’s you’ve created, you’ll be able to see the sharing parameter specified for the volume.





Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s