MetroCluster configurations provide data mirroring and the additional ability to initiate a failover if an entire site becomes lost or unavailable. The MetroCluster configuration uses SyncMirror to build a system that can continue to serve data even after complete loss of one of the sites.
Data consistency is retained, even when the data is contained in more than one aggregate.
Like mirrored HA pairs, MetroCluster configurations contain two complete copies of the specified data volumes or file systems that you indicated as being mirrored volumes or file systems in your HA pair. These copies are called plexes and are continually and synchronously updated every time Data ONTAP writes data to the disks. Plexes are physically separated from each other across different groupings of disks or array LUNs.
Note: You can have both mirrored and unmirrored volumes in a MetroCluster configuration. However, MetroCluster configurations can preserve data only if volumes are mirrored. Unmirrored volumes are lost if the storage where they reside is destroyed.
Unlike mirrored HA pairs, MetroCluster configurations provide the capability to force a failover when an entire node (including the controllers and storage) is destroyed or unavailable.
Note: If you are using non-mirrored aggregates in a MetroCluster configuration, the plex must consist of disks from Pool0. This is because using Pool1 disks for non-mirrored aggregate might lead to unexpected takeovers due to loss of connectivity between the two sites.
For more information about using the SyncMirror to mirror data, see the Data ONTAP Data Protection Online Backup and Recovery Guide for 7-Mode.