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How to calculate the overhead of storage pool based on the desired capacity when deploy a new ONTAP Select cluster or add capacity to an existed cluster

Last Updated:

Applies to

  • ONTAP 9
  • ONTAP Select
  • VMware Datastores


  • When deploy a new ONTAP Select cluster, you must to specify a proper storage pool capacity limit so that you can safely deploy and use the cluster.
  • The way to calculate overhead of the storage pool is different when creating a new select cluster or add capacity to an existed cluster.
  • When calculating the required minimum storage pool capacity, the following considerations need to be taken into account:
    • Capacity desired for the ONTAP Select nodes to be used.
    • Overhead reserved for ONTAP Select system backend operations: 130 GB - 272 GB per node
    • A 2% buffer is reserved for the total storage pool.


  • A 2% buffer is left unused in each storage pool, which is only used for available capacity check.
  • ONTAP Select virtual machines created on storage pools are attempted using thin-provisioning but are subject to underlying storage policies.
  • If honored, ONTAP Select will not immediately consume the full amount of the storage specified.
  • If ONTAP Select attempts to use storage that has been allocated to it and if enough storage is not available, a data-serving outage will occur.


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