# Introduction At some point in the grows of a database, there comes a need for replicating it across multiple datacenters. Reasons for that can be: - Fallback in case of a disaster in one datacenter - Regional availability - Separation of concerns And many more. Starting from version 3.3, ArangoDB supports _datacenter to datacenter replication_, via the _ArangoSync_ tool. ArangoDB's _datacenter to datacenter replication_ is a solution that enables you to asynchronously replicate the entire structure and content in an ArangoDB Cluster in one place to a Cluster in another place. Typically it is used from one datacenter to another.
It is not a solution for replicating single server instances.  The replication done by _ArangoSync_ in **asynchronous**. That means that when a client is writing data into the source datacenter, it will consider the request finished before the data has been replicated to the other datacenter. The time needed to completely replicate changes to the other datacenter is typically in the order of seconds, but this can vary significantly depending on load, network & computer capacity. _ArangoSync_ performs replication in a **single direction** only. That means that you can replicate data from cluster _A_ to cluster _B_ or from cluster _B_ to cluster _A_, but never at the same time.
Data modified in the destination cluster **will be lost!** Replication is a completely **autonomous** process. Once it is configured it is designed to run 24/7 without frequent manual intervention.
This does not mean that it requires no maintenance or attention at all.
As with any distributed system some attention is needed to monitor its operation and keep it secure (e.g. certificate & password rotation). Once configured, _ArangoSync_ will replicate both **structure and data** of an **entire cluster**. This means that there is no need to make additional configuration changes when adding/removing databases or collections.
Also meta data such as users, Foxx application & jobs are automatically replicated.