No, but ideally (and especially for live failover datacenters) it should be in a different wide-area synchronous grid segment[1] to prevent issues in the event of large disasters. For datacenters in the EU that means having a backup outside the continental EU, which has meant Ireland or Great Britain if they want to stay within the EU jurisdiction. With the UK leaving that means just Ireland.

Other disaster recovery concerns also mean that having large geographical distance between datacenters is a good idea. This can lead to jurisdictional issues, which need to be addressed when building the system.

[1] https://en.wikipedia.org/wiki/Electrical_grid#Wide_area_sync...