Consistency groups support any FlexVol volume regardless of protocol (NAS, SAN, or NVMe) and can be managed through the ONTAP REST API or in System Manager under the Storage > Consistency Groups menu item. Beginning with ONTAP 9.14.1, consistency groups can be managed with the ONTAP CLI.

Consistency groups can exist as individual entities—​as a collection of volumes—​or in a hierarchical relationship, which consists of other consistency groups. Individual volumes can have their own volume-granular Snapshot policy. In addition, there can be a consistency group-wide Snapshot policy. The consistency group can only have one SnapMirror active sync relationship and shared SnapMirror policy, which can be used to recover the entire consistency group.

The following diagram illustrates how you might use an individual consistency group. The data for an application hosted on SVM1 spans two volumes: vol1 and vol2. A Snapshot policy on the consistency group captures Snapshot copies of the data every 15 minutes.

Larger application workloads might require multiple consistency groups. In these situations, you can create hierarchical consistency groups, where a single consistency group becomes the child components of a parent consistency group. The parent consistency group can include up to five child consistency groups. Like in individual consistency groups, a remote SnapMirror active sync protection policy can be applied to the entire configuration of consistency groups (parent and children) to recover the application workload.

In the following example, an application is hosted on SVM1. The administrator has created a parent consistency group, SVM1_app, which includes two child consistency groups: SVM1appDataCG for the data and SVM1app_logCG for the logs. Each child consistency group has its own Snapshot policy. Snapshot copies of the volumes in SVM1appDataCG are taken every 15 minutes. Snapshots of SVM1app_logCG are taken hourly. The parent consistency group SVM1_app has an SnapMirror active sync policy which replicates the data to ensure continued service in the event of a disaster.

Beginning with ONTAP 9.12.1, consistency groups support cloning and modifying the members of the consistency by adding or removing volumes in both System Manager and the ONTAP REST API. Beginning with ONTAP 9.12.1, the ONTAP REST API also supports:

For more information about the ONTAP REST API, refer to ONTAP REST API reference documentation.

Beginning with ONTAP 9.13.1, consistency groups offer real-time and historical capacity and performance monitoring, offering insights about the performance of applications and individual consistency groups.

Monitoring data is refreshed every five minutes and is maintained for up to one year. You can track metrics for:

You can view monitoring data in the Overview tab of the consistency group menu in System Manager or by requesting it in the REST API. Beginning with ONTAP 9.14.1, you can view consistency group metrics with the CLI using the consistency-group metrics show command.

Consistency groups offer application-consistent protection, ensuring consistency of your data across multiple volumes or LIFs. When creating a Snapshot copy of a consistency group, a "fence" is established on the consistency group. The fence initiates a queue for I/O until after the Snapshot operation completes, ensuring point-in-time consistency of data across all entities in the consistency group. The fence can cause a transient spike in latency during Snapshot creation operations, such as a scheduled Snapshot policy or creating a Snapshot with System Manager. For more information in the context of REST API and CLI, refer to the ONTAP REST API documentation and CLI man page.

Consistency groups offer protection through:

Creating a consistency group does not automatically enable protection. Local and remote protection policies can be set when creating or after creating a consistency group.

To configure protection on a consistency group, see Protect a consistency group.

In order to utilize remote protection, you must meet the requirements for SnapMirror active sync.

Beginning with ONTAP 9.11.1, you can provision consistency groups with new volumes on a cluster within a MetroCluster configuration. These volumes are provisioned on mirrored aggregates.

After they are provisioned, you can move volumes associated with consistency groups between mirrored and unmirrored aggregates. Therefore, volumes associated with consistency groups can be located on mirrored aggregates, unmirrored aggregates, or both. You can modify mirrored aggregates containing volumes associated with consistency groups to become unmirrored. Similarly, you can modify unmirrored aggregates containing volumes associated with consistency groups to enable mirroring.

Volumes and Snapshot copies associated with consistency groups placed on mirrored aggregates are replicated to the remote site (site B). The contents of the volumes on site B provide a write-order guarantee for the consistency group, allowing you to recover from site B in the event of a disaster. You can access consistency group Snapshot copies using consistency group with the REST API and System Manager on clusters running ONTAP 9.11.1 or later. Beginning with ONTAP 9.14.1, you can also access Snapshot copies with the ONTAP CLI.

If some or all the volumes associated with a consistency group are located on unmirrored aggregates that are not currently accessible, GET or DELETE operations on the consistency group behave as if the local volumes or hosting aggregates are offline.

When upgrading to ONTAP 9.10.1 or later, onsistency groups created with SnapMirror active sync (previously known as SnapMirror Business Continuity) in ONTAP 9.8 and 9.9.1 are automatically upgraded and become manageable under Storage > Consistency Groups in System Manager or the ONTAP REST API For more information about upgrading from ONTAP 9.8 or 9.9.1, see SnapMirror active sync upgrade and revert considerations.

Consistency group Snapshot copies created in the REST API can be managed through System Manager's Consistency Group interface and through consistency group REST API endpoints. Beginning with ONTAP 9.14.1, consistency group Snapshots can also be managed with the ONTAP CLI.