# Synchronous Data Replication for VMware on Nutanix

Commvault provides a synchronous replication solution that builds on the Nutanix metro availability feature. The Nutanix metro availability feature provides datastore replication between an active site and one standby site. The Commvault solution enhances the Nutanix replication capability with enhanced management capabilities, backup copy operations, data retention controls, and additional options for the destination site.

With metro availability, you can provide data protection in the event of a site disaster. The Commvault software can track snapshots taken using metro availability on clusters in both sites, so you can have synchronous datastore replication across two sites.

You can use the metro availability solution with the Virtual Server Agent for VMware with IntelliSnap backups enabled and running on the Nutanix hyperconverged platform.

## Terminology

This documentation uses the following terminology.

### General Terms

Term | Definition
--- | ---
container | The datastore, where the data to be backed up is.
protection domain | The policy that defines the active site and the standby site.

### Terms for Sites

Term | Definition
--- | ---
standby site | The remote site or secondary site, where data is replicated.
active site | The site where the origin container is, and that contains the snapshot that is replicated. Active site is also called primary site.

Terms for States

Term | Definition
--- | ---
healthy or metro | The state in which both the active site and the standby site are active and enabled. In healthy state, when a snapshot backup operation runs, snapshots are replicated.
standalone | The state in which one site is down. Snapshots are not replicated.

## How Commvault Manages Snapshots in Metro Availability

The Commvault software manages snapshots differently, depending on the state of the protection domain.

### Snapshot in Metro State

In metro or healthy state, during the IntelliSnap backup, the Commvault software creates a snapshot on the active site and the Nutanix metro availability feature replicates that snapshot to the standby site. The Commvault software tracks both the primary snapshot and secondary snapshot in the Commvault database as part of the backup operation.

Snapshots on either of the two sites can be used for the backup copy, depending on which side is active when the backup copy runs.

A delete operation of a snapshot taken in metro state deletes snapshots on the active site and on the standby site.

### Snapshot in Standalone State

If the protection domain is in standalone state, the snapshots taken during this mode are registered only for the site which is in standalone mode.

Standalone snapshots can be used for backup copy only during the standalone state. When the metro state is reestablished, standalone snapshots cannot be used for backup copy.

Since only one snapshot is tracked during the standalone state, a delete operation deletes the snapshot on that site where the snapshot was created.

### Snapshots That Are Not Tracked

If you configure the Commvault software not to track snapshots, then Nutanix synchronizes snapshots between active site and the standby site of the metro configuration, but the Commvault software does not track the snapshots in the standby site.

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