Downgrade process considerations

You need to know about downgrade issues and limitations before downgrading clusters to an earlier version of ONTAP.

You should be aware of the following:

• For all other versions of ONTAP 9, you must perform a revert.

• If the version of ONTAP you are downgrading to has a different BIOS version than your current ONTAP version, contact support for assistance downgrading the BIOS before you downgrade ONTAP.

• Downgrading affects all nodes in the cluster.

• You can downgrade ONTAP nondisruptively.

  During the downgrade process, the cluster remains online and continues to serve data.

• If your cluster serves CIFS clients, nondisruptive downgrades are supported for Hyper-V and SQL Server over SMB solutions.

  These solutions enable the application servers and the contained virtual machines or databases to stay online and to provide continuous availability during the ONTAP downgrade.

  For all other CIFS configurations, client sessions are terminated. You should direct users to end their sessions before you downgrade to prevent data loss.

• ONTAP clusters can operate for a limited time in a mixed version state, in which nodes in a cluster are running different versions of ONTAP; however, the update is not complete until all nodes are running the new target release.

  When the cluster is in a mixed version state, you should not enter any commands that alter the cluster operation or configuration except as necessary to satisfy upgrade requirements. You should complete the update as quickly as possible; do not allow the cluster to remain in a mixed version state longer than necessary. An HA pair must not run an ONTAP version from a release that is different from other HA pairs in the cluster for more than seven days.