Managing datacenter server software licenses, as we all know, can be a challenge. One of those challenges is dealing with licensing terms and conditions related to backup servers. First, you have to know—what is the “temperature” of that backup server—hot, warm or cold. Licensing requirements are typically different depending on the type of backup in question. Licensing terms and conditions also vary from publisher to publisher and product to product.

Let’s try to define some terms—what do we mean by hot, warm and cold backup (or “standby”) servers? What about Active and Passive Failover?

-Hot Backup Server (may also be called Active Failover)— the server, in this case, is one that receives regular updates from the production server and is standing by ready (hot standby) to take over immediately if there is a failover event that takes down the production server. The primary (production) and secondary (hot backup) systems can run simultaneously in which case the data is mirrored to the secondary server in real time so that both systems contain identical information. In most cases, you will need a license for the hot backup server in addition to the license for the production server.

SOURCE: blogs.flexerasoftware.com