Your projects are hosted on dedicated server A (fixed IP A) and are configured with failover IP Z.
You may order a new server if server A isn't powerful enough to support your projects. Here it is described as server B, with fixed IP B.
1. You need to make copies of your projects and configuration files from server A to B. Then...
2. you can change the routing of failover IP Z from server A to server B. As your projects' data and your configuration files are linked to the failover IP, they will continue to work on server B. You don't need to make any configuration changes (DNS, APACHE, SMTP, POP3, MySQL ...).
You have two servers: A and B. Server A is your main server, server B is your backup server.
Your projects are configured on failover IP Z, routed to server A. You can regularly copy your projects from server A to B.
1. When server A is down, you can switch the routing of failover IP Z from server A over to server B. Server B is operational again, and it gives you time to fix server A.
2. When server A is fixed, you can copy the data of server B over to server A, then switch the Z failover IP routing again from server B over to server A. Server A will then be operational again.
The advantage of this solution is twofold:
It enables you to back up the data on server A
You can use server B of server A goes down
You can switch IPs from one server to another in the same datacentre. You can also switch IPs between different datacentres, if the datacentres is allowed if the data centres are located in the same country.