To configure the multi-writer option on a virtual disk, the disk must be in thick provision eager zeroed format. However, on NFS datastores that do not support vSphere APIs for Array Integration (VAAI), the only available format for virtual disks is thin.

If you use the vSphere Web Client to enable multi-writer on the thin disk that resides on an NFS datastore, the operation fails with the following error message:

Incompatible device backing specified for device '0'

1. Create a virtual disk in thick provision eager zeroed format by using the following command:

   vmkfstools -c disk_size[kK|mM|gG] -d eagerzeroedthick disk_location

   For example, vmkfstools -c 2g -d eagerzeroedthick /vmfs/volumes/myDatastore/disk.vmdk

2. To enable Multi Writer flag for sharing a particular disk, do step 2.1 - 2.4 below:
   1. Power off the virtual machine.
   2. In the .vmx file that defines the virtual machine, add an entry similar to:

          scsiX:Y.sharing = "multi-writer"

scsi1:0.sharing = "multi-writer"
scsi1:1.sharing = "multi-writer"
scsi1:2.sharing = "multi-writer"
scsi1:3.sharing = "multi-writer"

3. Save the .vmx file
4. Power on the virtual machine.

3. Add the disk to the appropriate VM that resides on the NFS datastore.