Specifying Disk ID to Set Size

When specifying disk sizes, you will need to specify the instance ID as well as the VM ID. The instance ID is the value of RASD InstanceID element of the virtual hardware section element describing the disk that should be resized.

<ovf:DiskSection>
   <ovf:Info>Virtual disk information</ovf:Info>
   <ovf:Disk ovf:capacity="4" ovf:capacityAllocationUnits="byte * 2^20"
      ovf:diskId="disk1" ovf:fileRef="disk1-file"
      ovf:format="http://www.vmware.com/interfaces/specifications/vmdk.html#streamOptimized"/>
</ovf:DiskSection>
<ovf:VirtualSystem ovf:id="vm1">
   ...
   <ovf:VirtualHardwareSection>
   <ovf:Info>Virtual hardware requirements</ovf:Info>
   <ovf:Item>
      <rasd:AddressOnParent>0</rasd:AddressOnParent>
      <rasd:Description>SCSI Hard disk</rasd:Description>
      <rasd:ElementName>SCSI Hard disk 1</rasd:ElementName>
      <rasd:HostResource>ovf:/disk/disk1</rasd:HostResource>
      <rasd:InstanceID>2000</rasd:InstanceID>
      <rasd:Parent>2</rasd:Parent>
      <rasd:ResourceType>17</rasd:ResourceType>
   </ovf:Item>
   ...

In the above example specifying instance ID “2000” (without quotes) would cause the disk with ID “disk1” (without quotes) to be resized: --diskSize:vm1,2000=256 (set the size to 256).

Note that if multiple disk devices are backed by the same disk (i.e. the OVF contains multiple disk RASD items that refer to the same disk) you must specify the new size for all disk elements, not just one. Sharing disks between VMs is not common, but allowed in the OVF spec.

Note that you cannot shrink disks.