One of the most fundamental components of load balancing or "reverse-proxying" is a Virtual Service. This may sometimes be referred to as a Virtual Server. The Virtual Service is an object that accepts requests and balances these across configured Real Servers. This ensures an application can scale and grow through adding additional Real Servers and can have redundancy if one server fails.

In addition to load balancing, the LoadMaster is typically configured to perform health checking of Real Servers to ensure that only healthy Real Servers receive requests. For further details on health checking, refer to the Health Checking Feature Description.

If one of the Real Servers fail the health check, the Real Server is marked as down and requests are then sent to the remaining available Real Servers.

If all Real Servers are down, the entire Virtual Service is marked as down and no new requests are received.

It is important to understand the difference between these two scenarios:
  • When a Real Server is down, users should still be able to access the application (assuming there is enough capacity provided by the remaining Real Server)
  • If a Virtual Service is down - no requests are accepted

The key to ensuring 100% uptime is to deal with any Real Server issues quickly before there is any user impact.