# CommServe LiveSync For High Availability Disaster Recovery

## Overview

The CommServe LiveSync feature keeps the CommServe server ready for disaster recovery and provides the ability to quickly failover to a designated standby host in the event of a disaster.

The standby CommServe host must be setup with identical software as the production CommServe host. Microsoft SQL Server Agent is used to back up and restore the critical CommCell databases from the production CommServe host to the standby CommServe host using the CommServe LiveSync operation. This reduces the downtime needed to recover the CommServe server, as the dedicated standby CommServe host is always kept in-sync with the production CommServe host.

One or more proxy clients are used to route requests and responses between the CommServe host and all the clients in the CommCell. When a failover is performed, the proxy client routes the requests to the standby CommServe host so that the clients can seamlessly connect and continue operations with the CommServe host. In addition, one or more clients can be setup to monitor the status of the active CommServe host and generate an alert when the active CommServe host is not reachable.

## Key Features

- Quick and easy installation of the relevant software needed for setting up the CommServe LiveSync feature on both the active and passive nodes.

- Microsoft SQL Agent automatically installed and setup with all the configurations needed to perform the LiveSync operation used to replicate the critical databases and keep them in-sync.

- Ability to use the feature out-of-the-box without any special configuration or modification.

- Ability to easily customize the basic setup using either the CommCell Console or the Command Center.

- One-click failover initiation and monitoring using the Commvault Process Manager.

- Support for Alert framework.

- Failover module does not rely on DNS or other network related services.

## Terminology

Production CommServe Host | The primary or the currently active CommServe host.
Standby CommServe Host | The secondary or the currently passive CommServe host. More than one host can be setup as a standby.
LiveSync Operation | The automated process of backing up SQL transaction logs from the production CommServe host and restoring them in the standby CommServe host. (This process is also referred to as Log Shipping.)
CommServe client | The generic term used to refer to the client or instance hosting the CommServe server. By default, the CommServe is installed in Instance001 on the production and standby CommServe hosts.
SQL client | The generic term used to refer to the client or instance hosting the SQL Server Agent used for the LiveSync operation. By default, the SQL Server Agent is installed in Instance002 on the production and standby CommServe hosts. Caution After the CommServe LiveSync installation, do not rename the client that has the Standby CommServe role assigned. Changing the client name disrupts CommServe LiveSync functionality and requires you to reinstall the CSLiveSync environment. To check the client properties, navigate to Manage > Infrastruture and click the Servers tile. The All tab lists all the servers in your CommServe server environment.
LiveSync subclient or CV Failover Log Shipping subclient | The subclient which is automatically created and used exclusively by the LiveSync operation to replicate the critical databases from the production CommServe host to the standby CommServe host.
Proxy or Proxy Client | A client (or clients) that is used as a proxy to route requests and responses between the CommServe server and the clients in the CommCell, before and after a failover. By default, the SQL client installed in the CommServe host is used as the proxy.
Production failover | Used to move the operations from the current production CommServe host to a standby CommServe host, for temporary or permanent operations.
Production Maintenance failover | Used for maintenance operations, such as installing a feature release, on the production CommServe host. When a maintenance failover is initiated, the production CommServe host is shutdown, and the standby CommServe host is brought online in READ ONLY mode, so that Clients can communicate with the standby CommServe host for restore operations only. Once the maintenance is completed on the production CommServe host, CommCell operations must be moved back to the production CommServe host by resetting the maintenance failover.
Test failover | Used to validate disaster recovery operations with the production Commserve host online and fully operational. When a test failover is initiated, ensure that the failover process succeeds and the services on the standby CommServe host is brought online. Backups and restores are not allowed from the standby CommServe host during a test failover. Once the testing is completed, a Test Failback must performed to shut down the standby Commserve host.

## Related Topics

Performing CommServe Migration from Windows to Linux

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