When you create a VMFS6 datastore, you can modify the default parameters for automatic space reclamation. You can also change granularity and priority or disable space reclamation for your VMFS6 datastore.


  1. In the vSphere Web Client navigator, select Global Inventory Lists > Datastores.
  2. Click the New Datastore icon.
  3. Follow the steps required to create a VMFS6 datastore.
  4. On the Partition configuration page, specify the space reclamation parameters.
    The parameters define granularity and the rate at which space reclamation operations are performed. You can also use this page to disable space reclamation for the datastore.
    Option Description
    Block size The block size on a VMFS datastore defines the maximum file size and the amount of space the file occupies. VMFS6 supports the block size of 1 MB.
    Space reclamation granularity Specify granularity for the unmap operation. Unmap granularity equals the block size, which is 1 MB.

    Storage sectors of the size smaller than 1 MB are not reclaimed.

    Space reclamation priority Select one of the following options.
    • Low (default). Process the unmap operations at a low rate.
    • None. Select this option if you want to disable the space reclamation operations for the datastore.
  5. Finish the datastore creation process.


After you enable space reclamation, the VMFS6 datastore can start releasing the blocks of unused space only when it has at least one open file. This condition can be fulfilled when, for example, you power on one of the VMs on the datastore.