Every virtual disk (VMDK) will have a normal (1,000) share value set on it, by default. The following procedure will help you modify disk shares on a virtual machine:

1. Connect to the vCenter Server using the web client and switch to the Virtual Machines and Templates view using the key combination Ctrl + Alt + 3.
2. Right-click on the desired VM and go to Edit Settings...:

3. In the Edit Settings window, click on the hard disk you intend to modify the shares and use the shares drop-down box to choose between, High (2,000), Normal (1,000), Low (500) or Custom (user-defined share value). Once you have set the desired shares value, click OK to confirm and exit: