Upon examining the server chart, we observe that when a web user accesses the domain, the traffic is directed to Cloudflare or other services before being redirected to our primary Web Server 1. The index.php file on Web Server 1 first checks the server load. If it is below a certain threshold (X%), the traffic continues to be handled by Web Server 1. However, if the server load exceeds X%, the traffic is redirected to Web Server 2, which may be on a different network.
Turning our attention to Database Server 1, we have implemented a RAID configuration to Database Server 2, along with a backup server on the same network. To enhance redundancy, we have implemented IP mirroring to synchronize the databases across Database Server 3 and Database Server 4, including the backup server.
While striving for a highly redundant network, it's crucial to note that this explanation serves as an understanding. When implementing this framework in our code, our PHP side must be prepared to support such methods. For instance, in the event of Database Server 1 being unavailable, the system will attempt to utilize Database Server 2. During this transition, the script will generate a "Loading page" for all SQL-involved commands, allowing Database Server 2 the time to recover and sync back to Database Server 1. Another scenario involves using Database Server 3, providing time for it to recover to Database Server 4 and subsequently syncing back to Database Server 2-1.