Multiple write action is disabled by default in VMware and you might need to enable this feature for some requirements when you are working with any VMware environment. I got this requirement for Oracle RAC configuration and requested to create shared VMDKs for their configuration.
Here, I’m going to show you how to create VMDKs and add advanced parameters to configure these disks as Shared disks, then simply you can add this shared disk to a different Virtual Machine and both Virtual Machines can write to the disks simultaneously.
I’m using VMware “Paravirtual Adapter” for this configuration, it has been designed to support very high throughput with minimal processing cost and it is the most efficient driver for my Oracle RAC configuration.
You can read more about vSCSI Controller performance differences from this this VMware Blog Article and You can read the Whitepaper for PVSCSI (Paravirtual) vs LSI Logic SAS IOPS Latency and Cost differences.
First of all, add a Hard Disk to your VM and note down the Virtual disk node as we need this node for the further configuration.

Once you successfully added the Hard Disk click on the SCSI Controller and Click on ” Change Type…” to change the controller type to “VMware Paravirtual”

Select the “VMware Paravirtual” as the Controller type.

Click on “OK” to apply the configuration

Go back to “Edit Settings” of the Virtual Machine, go to “Options Tab” , select “General” Under “Advanced” options and click on “Configuration Parameters…”

Add “SCSI2:0.sharing” Parameter (which we noted in the Hard Disk addition step) and value as “multi-writer”

Click On “OK” and Save the configuration. Now you have configured this VMDK as a shared disk and map this to your second Virtual Machine selecting “Use an existing virtual disk” and select the same SCSI node as the best practice.

Finally, do the same “SCSI multi-writer” parameter change for the second Virtual Machine and you are all set for the Multi writing to this shared VMDK. 

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