Setup requirements and restrictions for standard HA pairs

You must follow certain requirements and restrictions when setting up a new standard HA pair. These requirements help you ensure the data availability benefits of the HA pair design.

The following list specifies the requirements and restrictions you should be aware of when setting up a new standard HA pair:

  • Architecture compatibility

    Both nodes must have the same system model and be running the same Data ONTAP software and system firmware versions. See the Data ONTAP Release Notes for 7-Mode for the list of supported systems.

  • Nonvolatile memory (NVRAM or NVMEM) size and version compatibility

    The size and version of the system's nonvolatile memory must be identical on both nodes in an HA pair.

  • Storage capacity

    The number of disks or array LUNs must not exceed the maximum configuration capacity. If your system uses both native disks and array LUNs, the combined total of disks and array LUNs cannot exceed the maximum configuration capacity. In addition, the total storage attached to each node must not exceed the capacity for a single node.

    To determine the maximum capacity for a system using disks, array LUNs, or both, see the Hardware Universe at

    Note: After a failover, the takeover node temporarily serves data from all the storage in the HA pair.
  • Disks and disk shelf compatibility
    • FC, SATA, and SAS storage are supported in standard HA pairs.
    • FC disks cannot be mixed on the same loop as SATA or SAS disks.
    • Different connection types cannot be combined in the same loop or stack.
    • Different types of storage can be used on separate stacks or loops on the same node. You can also dedicate a node to one type of storage and the partner node to a different type, if needed.

      See the Data ONTAP Storage Management Guide for 7-Mode and the Hardware Universe for information on storage configuration options.

    • Multipath HA is required on all HA pairs except for some FAS22xx system configurations, which use single-path HA and lack the redundant standby connections.
  • Mailbox disks or array LUNs on the root volume
    • Two disks are required if the root volume is on a disk shelf.
    • One array LUN is required if the root volume is on a storage array.
    The mailbox disks and LUNs are used for the following tasks:
    • Maintaining consistency between the nodes in the HA pair
    • Continually checking whether the other node is running or whether it has performed a takeover
    • Storing configuration information that is not specific to any particular node
  • HA interconnect adapters and cables must be installed unless the system has two controllers in the chassis and an internal interconnect.
  • Nodes must be attached to the same network and the Network Interface Cards (NICs) must be configured correctly.
  • The same system software, such as Common Internet File System (CIFS) or Network File System (NFS), must be licensed and enabled on both nodes.
    Note: If a takeover occurs, the takeover node can provide only the functionality for the licenses installed on it. If the takeover node does not have a license that was being used by the partner node to serve data, your HA pair loses functionality after a takeover.
  • For an HA pair using array LUNs, both nodes in the pair must be able to detect the same array LUNs.

    However, only the node that is the configured owner of a LUN has read-and-write access to that LUN. During takeover operations, the emulated storage system maintains read-and-write access to the LUN.