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Rejoining split aggregates

You can rejoin split aggregates. You might want to do this if you have set up an HA pair in a MetroCluster configuration and a disaster breaks the HA pair.

About this task

There are additional considerations when planning to rejoin split aggregates that previously used MetroCluster to mirror SnapLock volumes.

Attention: When you rejoin split aggregates, Data ONTAP mirrors the data from one aggregate to the other and destroys data that existed on that aggregate before the rejoin.
You can use MetroCluster to mirror SnapLock volumes from one site to another. With proper configuration, the SnapLock volumes retain their characteristics at the mirror site. In case of a failure at the primary site, and if necessary, you can use the cf forcetakeover ???d command to break the mirror relationship and to bring the mirror site online. Once the failure at the primary site is resolved, the MetroCluster mirror relationship can be reestablished. The mirrors can be resynchronized before resuming normal operation.
Attention: The primary node might have data that was not mirrored before using the cf forcetakeover ???d command. For example, the data might have been written to the primary node while the link between the sites was inoperative. In such a case, you should back up the SnapLock volumes in the aggregate on the primary site, before resynchronizing the two mirror aggregates. This step of creating an additional backup for the SnapLock volumes is required to ensure the availability of all data.
For more information about backing up data in SnapLock volumes using SnapMirror, see the Data ONTAP Archive and Compliance Management Guide for 7-Mode.

For more information about MetroCluster deployment, see the Data ONTAP High Availability and MetroCluster Configuration Guide for 7-Mode.


  1. Determine the aggregate whose data you want to keep and the aggregate whose data you want to be overwritten.
  2. If the aggregate whose data is to be overwritten is online, take it offline by entering the following command.
    aggr offline aggrname

    aggrname is the name of the aggregate.

    Note: An error message appears if the aggregate is already offline.

  3. Re-create the mirrored aggregate by entering the following command.
    aggr mirror aggrname1 -v aggrname2

    aggrname1 is the name of the aggregate whose data you want to keep.

    aggrname2 is the name of the aggregate whose data you want to be overwritten by aggrname1.